1. Your emergency brake and parking brake would not hold. You have two? I've never seen a vehicle with two. Please provide more info.
2. Jacks don't work. Sounds like a burnt fuse. Check your fuse panel.
3. AC ~ that sounds like a failed wire. Most RV thermostats use telephone wires for control. These wires are very small and over the years can and do fail. Moving the wires around makes it work so you've got a break in one of the wires. Pretty easy fix, once you determine where the break is.
4. As for the engine going into limp mode, you'll have to provide more info as to engine mfg, size, etc. as well as the transmission info.....Dennis