Ignition system problem? Help!

This sure "sounds like" fuel to me.

One thing you can do is get a spark tester, start the car cold, determine that it runs "OK" and shut it down. Use the spark tester to examine the spark when cranking the engine, and take a GOOD LOOK.

Next time the car screws up, shut it off and retest the spark, and see if the spark seems deteriorated from cold.

"Rig" yourself a fuel pressure gauge temporarily BUT SAFELY!!! so you can monitor fuel pressure at the carb.