[travelin texans]

What will you be towing with? I would recommend a truck rather than a SUV for a rv that length. A 28' tt is pretty long to be in very tight spots in remote areas. Also a 4 wheel drive would be handy if in the woods alone with minimal cell service.
Wouldn't combine black/grey tanks, then it's ALL black. The grey will fill quicker & if off the beaten path & no one watching you could water trees/bushes with grey water, but once mixed you'll always have to find a dump station.
Don't know anything about a composting toilet, but sounds nasty!
One other thing to consider as well, most every RV park & most campgrounds DO NOT allow pitbulls or pit mix, along with a list of other breeds, something you'll need to ask before reserving sites.