Curious if you have vac advance on your distributor?
You mentioned easing into the throttle (vac advance would be pulling max advance still) and it runs fine.
Then you mentioned when throttle up aggressively you get the misfire (vac advance will not be helping the the timing will be retarded quite a bit).
You may have phasing issue in the dizzy where your too much advance or too much timing retard (your rotor is in between spark plug posts). This is a problem more common on small diameter distributors and can cause scatter and crossfire.
https://www.youtube.com/watch?v=aWMlNwGW0tM
Bad phasing and crossfire
https://www.youtube.com/watch?v=zulDzQ5q9TM
Everything You Wanted to Know About Vacuum Advance and Ignition Timing