Here is a
Ford vin decoder. Let's start there. Once you have that you need to go weigh your van with a full tank of fuel, loaded with all people, pets and gear that will be in it when towing. Take the gcwr you found for your van and subtract the scaled weight of your van. This gives you your adjusted towing capacity. The loaded weight of your tt will need to be less than this. Next take your scaled weight and subtract it from the vans gvwr to get your available payload. Your loaded tongue weight will need to be less than this number. You need to be below both of these and under your hitch ratings.
You also need to remember you will never tow a dry or unloaded tt. Knowing you are fulltiming and never had a tt, would shop using gvwr of tt for all calculations. Know thAt the average camper adds 1000-1500 lbs of stuff into their tt. (Plates clothes etc really do add up, we just took 1300 lbs of stuff out of our tt yesterday in prep to trade). In figuring your tongue weight, ideal tongue weight is 13-15% of loaded tt weight. AgAin you can use gvwr to calculate here.
Realistically, you will likely not be happy fulfilling in as small/light a tt as your van can probably handle. Remember lightweight tt usually sacrifices cargo space which means less space for your belongings and clothes. You may be happier with a motor home and toad or trade up your tv to match the tt or 5er that will fit your style. That said, you may want to rent a few tt in the size you can tow and we how they feel to you. Good luck