I'll assume the aftermarket Point-less Dizzy is not BOSCH, which is the only EI I would ever trust.
THE quickest and easiest "first step" is remove that Dizzy and put back the original Points type Dizzy after ensuring the points, condenser, cap and rotor are all up to spec..............I'm sure you'll notice a big difference
Let us know what gives!
After you do the above, whether good or not, a Mechanic's best friend is the humble VACCUM Guage..........learn to use its tell-tale "signs" and reap the rewards!
Cheers