Part throttle bog then backfire?

18degrees dist = 36 crank degrees. You need to fix the timing first then fix the carb. Shorten the slots to get around 22 crank degrees and use the factory light spring with an aftermarket light spring on the other side to start. After you get that sorted out you can turn your attention to the carb.

I think he's saying he has an advance limiting plate installed which limits mechanical advance to 18*. Like the one offered by FBO (J685 disc near bottom of this page) i have the same plate.

http://4secondsflat.com/Ignition.html