Wow. How have I not come across your build! Great unique idea on how to build it and your thinking is very similar to mine!
For mine, I went with a new custom frame, cause I was suggested against mating old metal to new for the tongue of the trailer, but I was more easily able to get rid of the drop that the frame does and keep it flat and level, and make a few custom mods. But I did give it a 2" body lift. I've also got the original trucks fuel tank mounted, and tucked it up to take advantage of the body lift. and I also got a 16 gallon take that's close to the same dimensions to put on the opposing side. As well with the space underneath, I kept the spare tires winch and put it tucked up under there.
I did the same thing for the receiver on my truck as you did on the trailer to have it flush mounted with the pin hole on the inside.
I also want a heater for the tent and, I was debating between propane and a fuel fire heater since I have the fuel tank. I was worried that the propane heated would suck back too much fuel. The Wabasto fuel fire heater takes about 2.5amps at max power but only uses .27L/h, and on a fuel tank at 8 hours a night, I could use it for 34 straight nights. That unit would cost over a grand however and for later on since I have a ways to go before I put heat in.
I did some work with my dad too. He did the torching cause he's a (retired) millwright and I have no experience with it, and was afraid I'd ruin the tips, and it was my cousin's set. He did burn one of my tail lights :S
Keep it up, it looks good!