Demon carb setup help needed.

Flip the carb over an look for a tiny screw around the rear throttle plate. I've had good luck with that in the past, tried it again recently and got a backfire in the exhaust system. Closed it back down, problem gone.

You probably need more timing. There's nothing wrong with 20* initial if that's what the engine wants, and it sounds to me like it does.
Unless I am blind which in this case I probably am... I did not see this screw. I read that some people will change this for an allen key so it can be adjusted while the carb is installed. I didn't see that screw. I will check again and see. It did seem to want more timing, but when I added some rpm the total was at 40 degrees or more.