A 50 percent water change, unless you absolutely have to, is I think quite a bit too much. And if you do have to change so much water, make sure the new water is at a decent temperature, treated with dechlorninator and if at all possible aged.
Heat going out in the house you can't do much about. Your heater is probably adequate, but if you are worried about the heat crashing again -- I know the feeling -- a second heater of about the same size would be fine.
Ich is ich. It comes and goes and it probably either came with a new arrival or after a particularly stressful time for the fish. The thing to do is get it early. Many people on this board recommend heat and salt to treat ich. I don't use this method as I can't get my water temperature high enough. Anyway, I'd just sit pretty. Things will go better. Tanks will just take on an almost self-sufficient groove, only requiring a minimum amount of maintenance such as a 10 percent water change each week. My suggestion to you is just wait and see. Don't get any more fish. Keep up with the water changes. See if you can minimize the sunlight and or overhead light a bit. Live with the algae for a time (get an uncommon plec, the commons grow too big) and enjoy your aquarium.
If you lived in Toronto, I could recommend you a great and honest furnace guy.
Jeff