I also run Prestone mixed 50/50. Many people have problems with the 220's over heating. Mine is pretty heavily modified and I had no problems even in mid 90's heat running a horribly tight harescramble (mostly 1st gear stuff). If there was ever a time it should have boiled over, that was it.
Oil mixture is a big preference thing. I generally go around 36:1, and I have no ryhme or reason for it. If it's gets colder I mix a little thinner (40:1) because it means I have more gas entering the engine and there for slightly richer jetting.
Pipe is another big preference thing. I am running an FMF rev pipe and like it. If I was starting over from stock I'd probably go with Pro Circuit. Since money is tight, don't worry about a silencer. The stocker is pretty good, just a bit heavy.
What gearing do you run? If you have problems climbing hills because one gear is too high and the next is too low you could go larger on the rear sprocket. Going to a 49 or 50 tooth rear will help to tighten the gear spacing. If you are having trouble stalling because you are in 4th gear when you need to be in 2nd, well, that's a riding technique you'll need to correct.