Dude - go back to fqactory settings and start from there- it sounds like your are really fat on top and bottom. its idling high because its not enough fuel being burnt off and its shutting off because the top is dumping to much fuel in while the carb is open. "make sense"
Go back to factory (including the idle needle)
When you tune make sure you are only going in 1 hour increments
high idle should not be a glow plug issue - its all in the tune
When you lean the low end needle it increases the idle and richening lowers the idle and your right its nothing the idle will do.
Hope this helps!
Oh I keep my fuel in my shed over the winter and never had bad nitro it always come back to tuning