For starters, who's been doing your work yourself or a Mechanic shop????
You've obviously spent some clams on it of late but have you replaced the air cleaner? Restricted air flow could be one cause for your symptoms.
Your timing is set at 20 degrees. Is this static? (at idle) If its static its to high & you could be over advice at speed. This would cause it to brake down & perform very poorly. I'd like to know more about whats been done to convert your distributor to electronic as well as this may have something to do with you issues.
I'd try dropping it back to 12 to 15 degrees & see if that improves this at all.
Your problem with it not starting on Gas could be as simple as a mixture adjustment, they are quite sensitive especially if your running a 300a setup or it could be a faulty part within the system itself but until you get the other problem sorted I'd not be looking at the Gas.