Like lowbuck said, it's pretty close to rebuild time especially since your cylinders are near 10psi different from one another but that isn't necessarily the overheating problem so you you might want to solve that problem first before you rebuild so you don't blow a new top end.
Do a leakdown test and check your impellar. Flush your cooling system to make sure there are no blockages. But yeah like everyone else mentioned, that is a symptom of a lean condition so try to find that for sure.