Final Draft 9 nights early October needs a look-over please!

Your itinerary looks all right. It's a shame you don't have more time in Munich as it's a 4 day minimum city. But the last few days of Oktoberfest is not the best time to tour the region. You might want to find a better place to eat than Hofbrauhaus, however.
I have still yet to hit the Andechs Brewery--southwest of Munich. I hear it's maybe the best beerhall of them all. Unless you've got extra days, I find Bacharach a great place to spend the night--but I have not found it to be a destination city on my three trips there.
And as far as visiting by rental car: You can see so many more sights and travel far more efficiently by rental car than by train in these parts of Germany.

Day 10 - drive to FRANKFURT for 10:30 AM flight

Be sure to set at least 2 alarms to make this really early hotel departure.

I guess you want to go to Rothenburg, not Rothenberg - I still would not spend 2 nights there, as Nuremberg has much more to offer. You can do the entire trip by train, but I guess a car does make sense to get to Rothenburg (and, possibly, Füssen).
On the Rhine, a cruise is best combined with a train ride (even if you have a car, it makes sense to return to the car by train rather than taking the ship both ways).

Your post indicates a real interest in WWII. If that is the case, check out a site named "thirdreichruins.com". It has many photos of Nurnberg, Munich, and even one or two of Bacharach as they looked during or just after the war. Then it shows the same places as they look today.

Thanks! We will definitely check out that site!

Also - we love beer and definitely will stop by Andechs Monastery after departing Munich if the weather is nice.

I think you probably don't have time for it, but a WWII site in the Rhine valley is the remains of the Ludendorff Bridge, the bridge at Remagen that the Germans failed to blow up and that US troops used to cross the Rhine. It has an excellent museum that tells the history of the bridge and the town. Nearby is the Chapel of the Black Madonna, which memorializes the US-run open-air POW camp for German troops.

Thanks I'll add the Rhine WW2 site to my "floating" itinerary.

Nuremberg is a very nice German city to spend time - many interesting sights and nice pubs - but I suspect you won't have much time to enjoy it with only one day there. I like Bamberg and Regensburg very much as well but why not just stay in Nuremberg on Day 7 instead? So many good options for a day on your own in town, a little something for everyone...

Brew pubs
Kunstbunker
Rock-cut cellars
Kaiserburg (Imperial Castle
Craftsman's courtyard
DB German Train Museum
Lorenzkirche and other impressive churches/buildings
Museums

Also, I understand having an interest in WW II, but 3 of your 10 days are dominated by Nazi stuff... Dachau + 3rd Reich tour + Nazi Rally Grounds? And right after touring a concentration camp you're pulling up a chair for dinner at Hitler's old hang-out...? Seems way too dark to me.

"All suggestions welcomed!"
I think this works better:

Day 1: MUC to Füssen by train (Bayern ticket day pass); 2 nights in Füssen
Day 2: In Füssen
Day 3: Train into Munich for the day and 1 night (Bayern ticket day pass) Stow bags in a locker at the station or drop at hotel there. Do the 3rd Reich tour or whatever interests you in Munich.
Day 4: Early morning train to Dachau Bahnhof. Stow bags in locker. Catch bus to Dachau KZ. Pick up car in Dachau for your trip to Rothenburg in the afternoon. OR - if you choose to drop Dachau - you can pick up a car in Munich and spend some time in the Romantic Road towns or elsewhere on your way to R'burg. Arrive in late afternoon in Rothenburg for one night.
Day 5: AM & PM in Rothenburg (this is plenty of time for this relatively small town.) Drive to Nuremberg for 3 nights. Arrive in evening, drop car ASAP - a car in Nuremberg is mostly a handicap.
Days 6&7: In Nuremberg. Possible day trip or half-day trip.
Day 8: DB Saver Fare train ticket to Bacharach or other Rhine town, 2 nights. (St. Goar or Bingen might be better if doing a cruise; Bingen is closer to FRA as well for your departure to FRA. Try the NH Bingen hotel in Bingen, right on the river with an awesome view.

No car is needed here. Bingen shares a train line with most of the Rhine towns of interest to visitors. The line follows the river the entire way north past all the scenery as it connects all the towns - Bacharach, Oberwesel, St. Goar and Boppard all lie just to the north. Rüdesheim is directly across the river - use the passenger ferry to get there from Bingen.

Stopover on way to Rhine? Würzburg is a great choice and station has lockers.

Day 10: Catch direct 6:48 RE train (€8.50) from Bingen Rhein Hbf station to FRA airport (7:33.)

Days 8 & 9, train transportation: The Rheinland-Pfalz ticket is a train day pass that covers a very large area. You could travel to all the Rhine towns mentioned and north to Remagen for that WW II museum at the Remagen Bridge site if you wish with this pass.

Thanks so much Russ I'm going to definitely look at this! I really appreciate the details (I need that). Are the train tickets easy to figure out / purchase at kiosks? It will be two of us.

"Are the train tickets easy to figure out / purchase at kiosks?"

The Saver Fare between Nuremberg and the Rhine would put you on the fastest trains available for this longer distance and would need to be pre-purchased online at the DB website for the best possible price. You commit to the time/day of travel at time of purchase. (Observe the refund policy and fees.) Looking at October 12 for example I see early morning options for two adults currently priced at €59.80, €79.80 and up. The price would be €134 - €174 if you bought these at the station.

The Bayern Ticket and the Rheinland-Pfalz tickets are day passes you can buy at the machines. There's a learning curve - so you can go to a ticket counter to buy these if you prefer personal assistance (€2 surcharge) in some places (many smaller stations do not have ticket counters.) Alternatively, you can pre-purchase these day passes online in advance for the exact dates you will use them and take them with you. That should work fine for a strict itinerary like you have for the Bayern Ticket trips. If you determine that you will be using a R-P ticket on a specific date you can buy that in advance too if you like (Bacharach, Bingen and the other Rhine towns have ticket machines but no ticket counters.) Day passes are non-refundable, so be sure all your details are right before you hit "buy".

Once in Füssen it would be possible there to pre-purchase Bayern Tickets and R-P tickets for future dates from the ticket counter there or from a ticket machine.

The final train ride to FRA from Bingen requires a RMV ticket, which you buy from a ticket machine in Bingen on the day of travel. RMV ticket machines have "RMV" on them. There are often combo RMV/DB machines as well:

https://www.rmv.de/c/fileadmin/_processed_/9/6/csm_Fahrkartenautomaten_nebeneinander_900x600_rms_Jan18_9e54f0b48a.jpg

Ticket machines like cash, but can be fussy with credit cards, so plan to have that amount available. They are fussy about giving back lots of change too - so have the exact amounts ready whenever possible.

Thanks again everyone and Russ I changed quite a few things around based on your guidance -- this will make the trip much more stress free!

I'm a pretty big fan of Deutsch Bahn's DB Navigator app for searching schedules and buying tickets. I have an AMEX account saved on it for ticket purchases. Once a ticket is bought, you have off-line access to it, so you don't need an active wi-fi/cellular connection to access tickets on your phone. I've used the app several times over the last few years to buy tickets, including throughout a recent week-long visit to the Rhine.

Thanks the APP suggestion came just as I figured out how to buy the train tickets from N to B (had some trouble with the website recognizing my phone number and displaying AM departures but google came through again). I'll definitely use the app.

Russ can you help me with planning our day and a half (2 night) visit to the Rhine? I'm going to post my question in a separate thread. I see you have helped a lot of people with train time schedules, where to grab lunch, get off here, get on there - which is what I really need. Really appreciate your guidance. Thank you

Sure. Include in your new thread any musts you have in mind. You can send me a PM if you prefer.