I am running a Midas 24 ft. (Freeport). 84' model.
Regarding your steering wheel controls, gonna have to get a test light and check things out there. A wiring diagram for that year chassis would really help. Look for a one ton van of that year and go from there. There is a good chance you will never get that cruise control, etc to work again, that was an old-tech system. Maybe you will get lucky though. I yanked my semi-truck OEM style Ford wheel off and put on a smaller Grant wheel....much better for my tastes.
Jacking...I assume you refer to a jack to change a tire, etc. No scissors style jack i have seen is gonna lift that much weight. For home-garage use, you need a GOOD floor jack or a 5 or even 10 ton minimum bottle jack, extra blocking and WHEEL CHOCKS for on the road use. That is a lot of weight and you do not want it to get away from you. Please note too, some chassis used left hand threads on the left side duals...and both sides are prone to having the lug nuts back off. Check them frequently. I am referring to the Ford chassis. You will not get the rear lugs off with a cheap little star type lug wrench either. The spec is around 200lbs for those nuts...high, yes but that's what everyone says. If they get just a little loose, you will break off one or more studs, and not even know it until you do a walk around at a fuel stop. Ask me how i know.
Your heater, you refer to the built in propane unit...yes? Either Suburban or Atwood most likely. That unit should warm up the interior within 10 minutes or less. Mine does, it's 19000 BTU. Unless you are in the 20's or less temp wise, maybe then it will have to work hard to keep up. Look for a label on the unit. I would have the furnace checked by an RV shop.
You need to take a careful look at the roof. Most of those are aluminum skin, one peice but the edges and vent areas need attention frequently. Search around here, there are lots of folks who have made repairs, it is not hard.
I'd go over everything, inside, out and underneath with a fine tooth comb. Or have a shop do it. At the age these rigs are, stuff happens. I had to replace battery cables, as well as some other wiring. Carefully check it all out asap. Don't get stranded somewhere because of a wire. Or worse, have a fire start. Most all these had 20 amp systems for the house wiring. It is very easy to overload the circuit with add ons, etc.
Oh, and your 10mpg...that is about it, even under the best of conditions. You are running a 351 Ford or 350 GM I take it. You might get 11-12 on very flat ground with no headwind and running 50mph. 60 mph or more and you are gonna watch the fuel gauge drop real quick. These all had 3 speed autos and 4:11 or so rear ends. Mine runs 2650 rpm at 50 mph. There are few places you can drive that slow anymore, freeways anyways.
Best of luck to you.