To be honest , for a single guy, a TT makes a world of sense I think, you can get a mid size unit 25' or so and be very comfortable. If you look on You tube you will find a ton of people living, albeit not always in the manner you would prefer, but living in minivans, so a 25'TT is well within reason for many. To use a Pickup for towing will give you the ability to take along a few toys which could be dirt bikes or a street machine, because Of your age when you retire, you will want to do things. So the truck gives a lot of flexibility.
If you are unsure about towing, learn, you said you have six years left in the service. I was In for 20 years, there were always people who I worked with at different units that were moving, so offer to drive a u haul truck and trailer and for one of them when they move.
Rent a truck, U-haul for a 4 hour rental charges $20 to rent a pickup, plus a mileage fee, the second time you do it, rent the cheapest trailer, do it on a Sunday and go to a local high school parking lot and learn to back up the trailer, with a mile of space around you and lines drawn on the pavement its the perfect way to start getting familiar.
You have the time, you could, if you decide the truck and trailer is the way to go, buy the truck in the next year or two to have it paid off before retirement, another potential cost savings, post retirement.
In answer to your secondary questions, you dont have to go "Uberexpensive" I would try to get a 3/4 ton truck, 4x if you want to off road some, but all the bells and whistles are just that, bells and whistles.
As to cost of a trailer they run the full range from very inexpensive (and therefore higher maintenance) to ultra high cost with proportionally lower maintenance down the line (hopefully). Much of the maintenance is the same with all. appliances, tires, batteries cost the same for basic or for premium, so find a middle ground.
If you are still thinking you want to go heavy boondocking look for larger tanks to maximize your flexibility.
Just get out there and try things, gain experience, and then you can make a better decision.
