Your fuel mileage sounds a little heavy...even for an RV. But those old Mopars, were never known for good mileage. Check for leaking vacuum hoses, or rich running. If you have changed the plugs, did they look dark (rich running?) or oil fouled.
The good news is you don't report he engine temp being abnormally high. Or it is burning oil. Or transmission slip.
But about the rough running. The earlier suggestions for wiring, plug issues are good. If they don't help, then think about a compression test. Could have a head gasket or valve issue. Although many times a bad head gasket will show water in the oil, white smoke (under load) out the tail pipe, High temperature, or other symptoms. A leaking valve will cause compression loss and rhythmic skipping, at all RPM's.
The A/C fridge issues can be cheap to fix, or very expensive. If it was me, I would research the engine issues first. If the engine is no good, I wouldn't put lots of money into fixing the other things.
The advice to replace anything rubber is good. But only after you get confidence that the rig can be saved for a reasonable cost. If you get the rig running good, then you need to make sure it will be reliable. Belts, hoses, Vac lines. Those things can be show stoppers if they fail on the road.
'12 F350 SB, CC, SRW, 6.7 PSD, 3.55 RAR, 6 spd auto
2015 DRV 38RSS 'Traditions'
Pullrite Super Glide 18K
Retirement = It's all poops and giggles....UNTIL someone Giggles and Poops.