electrical issues

Pull the yellow lead off the starter relay that's your ignition lead and check with key and a test light. Try in Park and Neutral. That'll rule out that. Could also bypass your NSS with a jumper and test it. Dim lights at idle are pretty common on these old cars. But wouldn't hurt to put a multi on it in the usual areas to see if your getting voltage drop anywhere. Test at the alt stud, regulator, across battery posts etc and see what your getting. Should all be pretty consistent and a good reading is between 13.8 and 14.4 volts. Any lower and your discharging, any higher and your over charging and will eventually cook your battery. 12.8 not running is neither here not there, just means the battery basically has a full charge at about 12volts.

A good option is relays for the headlights. Big upgrade to the old electrical system. Search crackedback (aka Rob). He sells a nice kit.

Good luck! I'm no electrical wiz, hopefully Rob or someone else has useful info for ya