Just some thoughts I have. I'm trying to go with your gut feeling that you thought it was some sort of ignition woes.

I suppose you already checked the connections of the AMM. I think it should start while disconnected but run on a fixed "limp mode" map in the computer.

You have spark but is it making it to the plugs?

Sometimes the rotor button goes bad that is under the distributor cap. It may look good from all appearances but if the resistor inside cracks, it is under a dark top coating, or if the button cracks down below on the keyed driver, its all over.

You might want to check to see if it all turns when cranked. It might be the distributors shaft or its gear is slipping. Give it a test turn by hand back and forth. Should be solid except for minor built in backlash.

Put in a old button. One that you know use to work but you changed it anyways, like a good boy does.

Then you may try this too! Throw a old plug into one of the wires off a another plug and lay it on the engine valve cover. It can help check the system.

When you looked into the oil cap hole and saw the cam turning that was a good thing. The next thing would be to have it stop with both lobes pointing up. The front cylinder lobes up and the crankshaft mark be on the zero mark.

If you want you can pop the distributor cap and make sure it is pointing to NO. ONE plug wire at the same time.

When you looked at the belt, were all the marks aligned? Or did you just pull the cover back and take a peek for shredding rubber fuzz. I was just wondering because that cover is hard to get off with the "V" belts still on. As I remember, one of the bolts gets blocked.

Have you ever looked at the plugs for gas fouling? No spark, usually means wet plugs.

If they are not getting wet. Well! An engine is like a woman and it just won't fire up! Spark alone won't make it do the hum. Like the old song says, it takes TIMING!

I believe I'll stop thinking now. Good luck!

Phil