Based on all of the responses (thanks for all your input!), it's loud and clear that I can never buy a TV that is 'too big' for towing an RV. What I have also concluded is that, although DRW's and the 8' bed add stability during towing, since my TT (and future TT) is just that (a TT and not a 5th), I could certainly scale down (F250 with SRW) and save a little on the expenses that come with a larger TV. For now, my F150 pulls our TT just fine, and I'm comfortable as long as we don't go across the country.
I left it with the dealer that I have pretty much decided not to move on this truck, however, I told him that coming down in the price would at least make us ask the question again whether we should consider it. Below is a link to the truck....based on KBB, the price is in line and is really at the limit of what we'd be willing to spend on another truck....I'd be interested to hear others' opinions.