ok its probably just the fuel then. Yes, definitely need at least 20% nitro. You will see a huge difference compared to the 10% stuff.
When you blow in the tube make sure the fuel goes into the brass intake.
If the temps are staying low you might want to use a hotter plug even with the 20%
You could touch the engine immediately after you ran it? How long did it run for? It doesnt sound like its even getting up to temp