I'm not sure what's going on with your heaters, but it sounds like something is wrong yours if it's overheating the tank. I've just picked up heaters for 75g and used it in my 60 with out any hot/cold issues. I think I picked it up at Petsmart but I forget the name of it. I got it when those Marineland ones were recalled.

You could also get a controller like a RKE that would shut your heater off in case the heater went bad. As far as a generator goes, you can go to Home Depot and pick one up. I got a Gereric (or something like that) 5500 but that will do most of the house. Also look at some pawnshops and see what they have...sometimes you can find a good deal.