There is no such thing as "Topping off" a propane tank to absolute full. For safety purposes, propane dealers only fill to 80%, because excess heat will expand the contents, and make a potential bomb out of it in a short amount of time.
I own, and ride a really nice 2003 Kawasaki KLR 250 that seems to have all the power/speed anyone would need for a trail bike, or on a county road. I like it because it is about 100# lighter, and 6" shorter than the KLR 650, and is easier to keep upright in rough conditions.
It seems like you should stay in Florida, but find a nice small town with available section 8 housing towards the middle of (away from the super busy coasts) Florida...your housing will be cheaper, it will be quieter, there will be less people, with a much slower pace. Use you van for the...
I have seen people doing buildouts in the Lowes/Home Depot/Menards lots as long as they are getting supplies there...not a place to overnight, but a good open space that you could set up a generator, and work table.
A small 12 volt circulation fan mounted up near the ceiling will pull some of the warm air down towards you...run it on low, and it won't even really make a noticeable breeze.
Do you NEED to leave central Florida, you are just coming into good weather in your home state. Look into spending your first Winter poking around on BLM land in Fla rather than the big trip to Arizona.
Do some practice runs in your driveway/yard, and then work yourself up staying in a campground before you try out off-grid boondocking in remote locations. You will need to pare down many possessions along the way in preparation.
Lots of adjustments to make on the hitch, and bars to prevent that. If it is behaving badly, slow down, and don't jump on the brakes. Wind gust, and pavement variations will contribute to the problem, as well as passing semi trucks.
Ironically I hear many of you complaining about someone camping too close to you while on BLM land...as if you have some God given right to your own elbow space. Maybe those complaining should camp at a State Park where the sites are clearly outlined.
As a land owner, I don't want van dwellers...
Cam phasers were a problem on the earlier 5.4 motors. It would indicate a problem with a loud ticking sound, that should also sound like another common problem...exhaust manifold gasket leak. The spark plug problem can be eliminated by properly torqueing the new plugs, but follow the procedure...
My choice would be a 16x8.5 with a "V" nose cargo trailer. The 8.5' wide is due to the wheel wells being inside, rather than fenders that stick out the sides. You could have a full kitchen up front, and a fold up bed, while still being able to bring your motorcycle, and kayak along for far less...