I'm starting to think that a 14cc milled .65 was a bad choice
This is simply a learning curve your on right now.
And you seem to be picking up some pointers as you go.
Generaly I sugest street engines not exceed 11:1 and stock cams are best for less than that to prevent detonation.
You could use a thicker head gasket, but that may not be enough to prevent trouble.
Is there E 85 in your area?
You may have choice of fuel thats not going to cost you much.