Though I'm not at all familiar with your engine, you might try leaning the idle needle at bit. (Since it is inverted it'll load up quicker at idle than if it were upright.)
I once saw a .07 ABC engine that simply ran too hot. Didn't seem to run right no matter what we did. The owner switched to 20% all castor, raised the tiny tank a little, and it now runs cooler without the previous problems. I mention this since your engine may run better on a little more castor in the mix.
You probably should also:
-check for air leaks and seal anything that is suspicious
-check pressure fitting in tank to make sure air flow is not impeded in any way
-try a new glow plug
-flush out main needle barrel backwards to remove possible blockage

I realize these may be elementary things that you have already tried but sometimes we forget things.
(I had an upright engine doing very similar things. Turned out a piece of the main needle O-ring had lodged itself between the needle and it's sleeve inside the carb.)

Good Luck and tell us what you find,
Jeff