Hi Dennis! Okay so I'm assuming that you have an early car? Yes the alcohol eats the insulation on the coil windings & they just stop working.
The Idle screw didn't have a cap on my T/B. Usually no one knows it's there, on the underside out of site as it were, so the screw usually escaped people messing with it. If you know it's there, you know not to mess with it!
Your symptoms seem to be temp dependent to a large degree. Do I read you 5 by 5 on that? This is the way I would approach this issue. If you have a scanner, hook it up and drive with a co-pilot until the car acts out and then look at the displayed data. Me I work alone so that don't work too well, trust me on that one! If you're in the same boat then hook up the scanner and wait for the symptoms to appear or induce them if you can & observe the scanned data.
In any event I would read the section on Intermittent troubleshooting in section 6. JMHO!
Tom