Thanks again for the info!
I was penning this message as you responded. Sorry for the rapid fire but I am emotionally distressed by my motorcycle at the moment.
In retrospect I think my tiny battery has to go. I think I'm going to replace everything that can easily be replaced, and hope that fixes it... The plan is to eliminate all possible variables, and so far that includes battery, ignition switch, coil, plug cable, and TCI box.
I'm considering the MB7BB 12v 9ah battery since it's only a half-inch wider than the 7ah. The 2.4ah has been fine for my kickstart, but I do complain about electrical issues a lot, so I want to eliminate this as a variable. I have my battery sitting up under a custom seat, and I think fitment will not be an issue. However, maybe I try out the new coil first and see if that does it.
My ignition switch has been on the fritz for years. It is better than before with the resolder I recently did, but in the off condition it is still letting 1.5v through. And in the on position, I am losing about 1.x volts at the switch itself, which is 10% of my battery power.
There is a dealer who carries Enfields not too far from where I work so I'll give them a call and see if they have the green TCI and Ignition switch in stock. I already have the green TCI, but it's cheap enough to replace, and worth it to me for piece of mind.
There are replacement wiring harnesses available on ebay and amazon, but the sellers look suspect, and I don't want to get something that's worse than the OEM harness (!). I don't have the time or knowledge to rewire one by hand though, so maybe if the component replacements don't do it, that might have to be my next plan of attack. I do have some friends with some electrical know-how, so perhaps they would be up for digging into the harness on a weekend with me.
Honestly I have spent next to no money on maintaining this bike besides oil and a few replacement parts along the way. Sinking a couple hundred into it right now is a drop in the bucket compared to buying a new modern motorcycle. Plus I love this Enfield and I have poured my heart into it for the past 8 or 9 years, even if it hasn't always returned the favor. I'll do everything in my power to get it running reliably (to use as a daily commuter). If by January I haven't reached that point, maybe then I'll have to take it off of registration and insurance, buy a new japanese bike, and keep the enfield as a fixer-upper.
Tooseevee, I will look back on your build/troubleshooting threads to read up on all the information that led you to your current equipment selection.
Wish me luck, Gurus. Advice is always welcome. Thanks and cheers.
Chuck