After seeing what you have for power in the old TT, you will be using the generator daily. The solar won't recharge your batteries each day, especially if you use the inverter. They will be sucked-dry quickly by the inverter. Also, if you use the heater, it will draw the two batteries down quickly.
We only dry camp. We go to some remote spots that a 5th-wheel would not fit down the road (overhanging/leaning trees are the biggest challenge to full-height trailers). Two 110ah batteries, 200w solar, no generator. No problem doing 9 nights in a row.
I would keep the second trailer, just as you indicated. But, be sure to have enough fuel for the genny, as I believe you will use it daily. You may soon decide you don't want to use the genny if you are out in the boonies with all the silence. If that happens, two larger batteries and at least 200w solar (more, if you really want to use the inverter for a while) are in your future, if you want to invest in that.
There are many Forest Service roads in the west that you could get your fiver down, with pull-outs to camp in. But, many of the roads are fairly rough, and you may not want to pull the fiver too far on them, due to the beating it would take. Not sure about Forest Service roads in the east, though.
Good luck on getting the DW to go dry camping! My wife prefers the boonies, and doesn't like campgrounds when we have the need to use one.