I had the head wrapped with foil tape as well.
It was sounding like it was running hot when I was first reading through your post, and then I saw the quoted phrase and am more convinced that this is the case. Not allowing the head to cool is likely to cause problems and not solve them.
Since the engine has never run correctly, I'd suggest looking through your entire fuel setup as a starting point. You may have a kink, a blob of crap in the tank or a small hole in the fuel line or any of a number of other problems. Do you have a more experienced flyer in the area - perhaps in your club - that can lend a hand to get the engine running correctly in more normal temperatures before trying to adjust for cold weather?