You need to be looking for custom off road RV's for the type of camping you are looking to do IMO.. ;)
And those aren't going to come in anywhere close to your budget, even used...
If you are towing anything, even in the best of weather and towing conditions and setup, you should not be "focusing on my audiobook"... ;)
Even a seasoned RV'er would have a hard time with your requests as there aren't gonna be too many 15-20 year old rigs that are going to be able to live up to the conditions you have slated and even if they are, the maintenance and upkeep on it is going to completely outmatch your experience with it..
I wish you luck in your endeavor.
Mitch