You need to check for a vacuum leak. Put your hand over the carb and see does it smother out or continue to run. You may also need to fatten the jets in the carb. You should be able to run at least 32* timing no problem. Seems to me you should be pulling a little bit more vacuum, but I don't know the LSA of your cam. I think it's 10, It should be at least 12 and even better at 14. The blower is going to kill some of your vacuum because its still putting out a positive pressure, just not enough to overcome the engine's vacuum. It can't pull enough air with the throttle shut. I really think it'll run better if you put the stock crate engine cam back in it.

Tech should be able to give you a lot more info, I'm still new to the blower technique myself.