Layovers

With a IAH-AMS-FCO and FCO-AMS-IAH itineraries, you will be going through immigration both ways in Amsterdam. (Entering Schengen and departing Schengen). So make sure you have enough time for that. Exit immigration doesn't take long it just depends on how many people are ahead of you.

If for some reason, you are delayed and miss your returing flight to Houston, it is the responsibility of KLM to get you on the next available flight. And if you have to stay, they will pay your hotel expenses as well as giving you compenstation.

Airlines don't offer connecting flights unless there is time enough to make the connection.

KLM is part of a combine headed by Delta (maybe called Sky Team) where you can weirdly get the best prices by booking on one airline and flying on another. If your KLM flight number has 4 digits, odds are you will not be flying KLM.

To stay a day or two in Amsterdam is not a layover, its an open jaw flight, usually called multiple destinations on booking web sites (choose whatever the alternative to round trip is)..

Start your search for flights on Kayak. Then go to the top three best priced airlines own web sites to narrow it down. And check trip travel time on Kayak because the best price usually turns out to be something that requires 8 connections and takes 31 hours.

If your body can handle it, I would absolutely book the 9 hour layover on your way out. That will give you plenty of time to see Amsterdam or other nearby areas during your layover if you wish. 50 minutes on the return should be okay. First, airlines typically give themselves additional cushion with arrival times. Secondly, AMS officials will often allow travelers with short connection times to enter a short queue for quicker clearance. Lastly, if you miss your connecting flight KLM will put you on their next available flight automatically, so you can just roll with it all.

2 or 9 hours would be my choice. I have had a few 8 hour layovers that I went into town and sightseed. It's better if you don't arrive at 6 a.m. A lot of things don't open until 9 or 10.
They have (had) physical lockers in the airport, but you can also drop any hand baggage you don't want to carry around at the left luggage department at the main train station. I would ensure that you have added a luggage lock to relevant zips, however.
I have so many flights that are delayed, I just wouldn't want to have a 50 minute layover.
I also don't agree that all transfer times posted are considered 'doable'. There are rules of minimal times, but sometimes a matrix online fails.
As an alternative, have you used a search engine like matrix ita website? it is the old travel agent flight search system that went public a number of years ago. Then you go and buy from the airline's website.

we have made numerous flights to Europe and early on we realized we are missing out by not staying over in those "fly through" airports (my term). Since then we have decided to add a short stay to each, ie.. Rome, Paris, London and Amsterdam. This year we return through Amsterdam and decided to stay over Amsterdam is a 100 euro from London when books separately. Once we committed to Amsterdam our two day stay soon became 5, not counting our in and out days, once we started reading up on RS book. Lots to do, Anne Franke, Van Gogh, Riksmuseum, nearby towns The Hague, Haarlem, Leiden etc. Last year London was the same and "the Tube " underground takes you everywhere.
PS we almost always start by using Expedia and look for Non stop flight from our home town to a major city in Europe that arrives in the morning hours then plan to be outside most of the rest of the day.
Safe Travels

Several years ago, I had booked flights months ahead with a "legal" connection time planned at Schiphol, maybe 55 minutes, but the second flight got rescheduled to depart earlier, making the layover only 45 minutes. I did make it, and so did my checked luggage, but with the help of the transfer staff calling the baggage folks and me almost running through the airport.

I've also decided that I don't like getting a taxi at 4 a.m. for a those early departures from Rome, so I sometimes choose to depart later, causing an intentional "disconnect" and spend a night in Amsterdam (paying for a hotel). I don't believe that the longer layover necessitates picking up your checked luggage.

For years I have been asking whose laws make a "legal" flight connection. And if the flight connection doesn't work, what authority enforces that "law"'? Airline computers may 'think' a tight connection is okay but can't allow for airport congestion and delayed arrivals. Even if a mad dash does bring you to the second departure gate before it is locked shut, your luggage may still be on the ground. Twice I have had my suitcase left behind on tight connections, both from an international to an internal flight. In both cases the left luggage was delivered to my hotel relatively quickly, once in a different country, which probably ate up the airline's profit. So to me, the only legal connection is the one you can make with relative ease.

Since the tight connection is on the homeward-bound flights, checked baggage should not be a deal-breaker. Once you get home, you can wear clothes out of your own closet (clothes from the checked bag will most likely go straight into the laundry anyway) and the airline will deliver the bag(s) to your home, probably the next day. One of our bags decided to spend an extra day in Paris on our last trip -- and that was without a tight connection.

Tip for lost suitcases : Use a suitcase that has an unusual pattern on it. Take a picture of it while on the scale at the departing airport.
If it's lost you can show the picture (on the scale to proof you checked it )and the airline employees forward the pic to whomever is in charge of that.

wow, lots of recent responses! well, thanks all for the advice because i decided to book the flight actually! possible updates to come, lol...but yes, i figured having your bag lost on the way home is much better than the way there!