Usually the "adjustment" on those is only slight - it's just Fine Tuning.
FIRST you need to determine IF it's a fuel or Ignition problem. THEN you track down WHAT component is faulty - IF one is, or what is CAUSING it.
There are probably 3 dozen items/reasons WHY you are having trouble. But probably only ONE is causing it.
Questions - the distributor is connected to a vacuum source that has very little or 0 vacuum at idle, then slowly increases with RPM? That's ported spark vacuum - no matter what a label says - check it!
Make sure it is really getting to the distributor.
And - check base timing - vacuum disconnected - it should be around 8.
Check total timing at 1500 RPM, again at 2000, and at 2500 RPM. Tell us what it is. Too fast, too soon, or too much can cause your stumbles.
Plugs - you ARE using the STOCK ORIGINAL BRAND AND PART NUMBER plugs, not junk aftermarket parts houses love to sell because they make more $. Are you? Wrong or Mickey Mouse plugs can do it - especially since you say it gets worse warm.
No splits, plats, multi's, Kraut, Jap, or any other gimmick plugs. Use what the designers of the head designed the head around. Look in the book!
Contrary to popular belief - what type of fuel system, or what generates the spark has NO BEARING on how the plugs act in the combustion chamber. They don't get longer, change heat ranges, or change indexing just because you have a different coil or carburetor.
Don't go throwing parts at it - changing stuff arbitrarily will not do much more than changing tire pressure will help. (But a couple of STP stickers might.)
It ran fine once, it can again.
Do it and report back for the next step(s.)