It's hard to say, but it might be the ignition or vacuum if I had to guess.

You know you have spark, but under compression pressure, more voltage is needed to fire the plug. I vote for a bad ignition rotor, it's a maintenence item, and can look good and still be bad.

I would also check the plastic vac line that feeds the brake booster, when they break, they can cause a intake air leak large enough to cause a no start. I've seen it before.

Good luck.