Take the trailer home, load it up like you were going camping, take it to the scales and get all the weights, go home and setup the WDH hitch, go back to the scales and confirm the weights, adjust the WDH again, weigh again, take it for a test drive, take it home, unload it, take it back to dealer, try a different trailer and repeat process until you get one that tows okay loaded the way you want it.
Seems like too much work, I think you should get a F150 and trust the salesman trying to sell you a trailer. You will be fine.
In all seriousness, do your homework, work the numbers best you can and buy a trailer within the limits. My opinion is that payload is what will limit what you can tow (at least for bumper pull travel trailers). If you try and reduce the tongue weight to be within specs, you could end up with sway from too not enough tongue weight...
If you do all your homework and settle on a trailer, you might be able to make the purchase contingent on being able to tow it with the tow vehicle and setup you will have.. never tried it but might work.