Normandy - Need help!! Itinerary reco & tons of other ques!

If you can accept the fact that you might run into snow and ice on the roads and your daylight hours will be short, go ahead with your planning keeping in mind this is seacoast in winter with rain and fog and very little sun light. Most important is to check opening hours of places you intend to visit.

I can only address a few of your questions. I haven't been to Etretat or Mont-St-Michel.

I think a D-Day tour is an excellent idea for most people. I think the cost is about 100 euros for a full day, and the driver/guide will get you to far more places than you'd manage by yourself, plus you'll have the benefit of his/her explanations. Most of the tours depart from Bayeux, so it is extremely convenient to be staying there the night before. But Bayeux has several top-quality sights (the invasion museum, the cathedral, the tapestry, plus the historic center), so multiple nights are certainly justified. I took a walking tour offered by the tourist office and enjoyed it.

To me Rouen and Bayeux are very different. Rouen's (rebuilt after wartime destruction) historic district is large and gorgeous. There are several good museums. You'd need to research the parking situation there.

Just from the map perspective, it seems to me you'd be better off starting in Rouen and ending in MSM or vice versa, rather than going straight to Caen (which is in the middle of the territory you're interested in) and consigning yourself to a lot of extra driving. You could take the train to Rouen and not pick the car up until the next day, after completing your local sightseeing. However, I don't know anything about how easy it is to pick up a car in Rouen, nor do I know where you'd be able to drop off the car near MSM/Pontorson. Of course, driving back to CDG and returning the car there would be an option.

I see that one of the route options for the Pontorson-CDG drive offered by ViaMichelin.com takes you right past Fougeres and very near Vitre. I thought both of those were very picturesque towns, worth several hours of wandering around--though I doubt you'll have any extra time.

At that time of year, a lot of hotels and restaurants in Arromanches will be closed so I’d opt for Bayeux as a base. If you do so, see if you can stay on MSM for your last night to avoid doubling back and forth.
I found Bayeux to be a great home base. Easy to visit the WW II sites, the great little museum in Arromanches and the museum in Caen. If I had the time, I’d consider visiting Honfleur but Etretat is a bridge too far...

In Bayeux I stayed at the Chateau de Bellefontaine. Beautiful building, large rooms, good breakfast, on the outskirts of the city but free parking and convenient for getting into the town center or visiting other areas. One of my favorite restaurants in France is Le Rapiere, not inexpensive, but excellent!

I’d suggest checking with AutoEurope, highly recommended on this forum, for car rentals. If there’s no extra drop off fee, or if it’s low, I’d consider driving back to CDG. Otherwise you’ll have to return the car, take the train to Paris and then the RER to the airport, a real PITA.

I would highly recommend signing up for one of the professional tours of the DDay beaches. As acraven said above, it will enhance your experience immeasurably.

Having visited the D-Day beaches and American Cemetery without a guide, I agree it would be better to take a tour if you want an in-depth explanation of what you're seeing. If you do go on your own, the American Cemetery has a free walking tour (I think at 11 a.m.) but don't be late because (according to our experience) once they start off you will not be able to catch up with them.

There's more to see in Honfleur than Etretat, and it's more likely to have accommodations open year-round. (However, I'll admit to not really visiting Etretat, due to parking issues on a sunny Saturday in October.)

I started in Paris, took an early direct train to Rouen and rented a car there. After a half day walking Rouen's center, I drove to Etretat/Fecamp. I booked a room with a private bath at an Airbnb (not expensive, free parking). Checked in there then walked the cliff trails through sunset. Half a day was probably enough.

The next morning it's a short drive to Honfleur. Look around through lunch time. I skipped Honfleur only because I planned to see port towns in Brittany. I think you should see Honfleur. A good base is Caen. It has more to see than Bayeux and you can catch a D-day tour from there just as easily. I'm not a WWII fan so my visit to Bayeux was to see the tapestry.

It's about 1 1/2 hour drive to MSM from Bayeux, probably about the same from Caen. I'd suggest arriving early enough to visit the Abbey at the top of the island. As I recall, it closed at six when I visited (mid-September). It will probably close much earlier in January. I'd plan to get there midday and stay until dark (you will have four or five hours max).

You could return the car in either Caen, Rouen or Rennes and take a train back to Paris fairly easily.

Remember in January the weather is likely cold, wet and windy (anything else would be a pleasant surprise). The sun goes down early. It will seem to get dark even earlier when it's overcast. Dress with that in mind - water proof not water resistant and good warm layers underneath. I think I'd like to have a rain shell over my pants too, umbrellas and wind don't mix well, and shoes that keep the water out.

In January, open hours will be much shorter and fewer restaurants will be open. The good news is, unless it's unseasonably nice, you will have the place mostly to yourself - so working around tourist mobs won't be much of an issue.

I disagree with Brad that Caen has more to see than Bayeux. Caen was virtually flattened during the war so has little historic architecture, whereas Bayeux's historic center survived intact. Each place has a major war-related museum. I liked them both, but a lot of people find the Peace Museum in Caen overwhelming. It's crowded, expensive and pretty much a full-day affair because it covers the lead-up to the war, the war itself and the Cold War. The Bayeux Museum focuses on the war in Normandy and can be visited in a few hours. Bayeux also has an historic cathedral and the tapestry. Several people have mentioned the British Cemetery in Bayeux, which is out near the museum; I did not have time to see it.

The Peace Museum in Caen offers D-Day tours, but I believe they spend part of their time in the museum, so you don't see as many invasion sites as you would on the other full-day tours, most of which--as far as I know--depart from Bayeux.

I based in both Caen and Bayeux because I did not have a car. Caen is a very good hub for public transportation, and I day-tripped from there to Cabourg, Deauville and Honfleur. Visitors with cars will not benefit from Caen's bus and rail connections.

Caen is a living city, not a tourist town, and that is an attractive characteristic, but I think most North American visitors would be a lot happier with the environment in Bayeux despite the presence of many tourists.

What acraven said re: Caen. Not much to see there unless you just like hanging out in a post-modern industrial city. Bayeux has way more charm and sights. And is slightly more convenient to the D-day beaches and sights.

Regarding Mont-Saint-Michel, I vote for a stay on the island. Yea, yea, yea, the view from the distance is great. However, you can get that same view going to, and coming from MSM. But the intimate views on the island after dark, with no crowd of tourists is the cliché "magical." And whereas MSM is on the SW distant point of Normandy, returning a car to Rennes is a great way to wrap up the trip logistically (maybe with lunch and walk-around there). If you want one more WWII reference on your trip, the American Cemetery in Saint James holds almost half as many deceased, but one-tenth as many tourists, and it is en route from MSM to Rennes.

With 5 full days you have plenty of time to put a nice itinerary together for Normandy.

Train from Paris to Rouen takes most times no more as 1½ hour. You can visit it in the afternoon, evening and the next morning. After picking up your car you can drive to seaport Fécamp and follow the scenic route (D211 and D11) along the coast to Étretat. You can stay there or drive in the evening to Honfleur.

From Honfleur via the coastal road to Deauville and further to Bayeux with a stop in Beuvron-en-Auge. If having time you can visit that famous tapestry the same day.

Next day D-Day tour and drive to Le Mont-Saint-Michel and arrive there at the time that the crowds are gone, however no idea if there are serious crowds early February. Next morning still enjoy this island and drive further west to Saint-Malo and Dinan. The route between Cancale and Saint-Malo is scenic.

On the way back to Paris as already mentioned Fougères and Vitré are really nice historical places, Further the historic centre of Le Mans is much overlooked, but stunning. You can spend the last night in Chartres before going back to Paris.

This is just a rough idea, there are a lot of nice spots between the mentioned places to fine tune this itinerary.

A reasonable priced hotel in Bayeux is Reine Mathilde. Nothing special, but great location and clean. Wonderful restaurant.