Holy cow....that is some good work! Like, 80% of your list I still need to do to my W123, and I keep putting it off...

Nice man!

As far as the electrical system goes....Check the basics first, and check the fusebox that is under the hood on the drivers side. Some people have reported difficulties getting the lid off, since you need to kinda twist it to get it out. I personally never have had a problem, it's pretty damn straight forward.
Anyway, check your fuses. They should be copper. In most of these cars they have been replaced with metal ones at some point, and the metal corrodes the fuse box and introduces all kinds of nasty electric gremlins.

The solution? Buy all copper fuses (you can get them on this website, they are dirt-cheap), throw away all the old ones and sand the contact points on the fuse-box lightly, to get rid of the corrosion.

__________________
"The MB W123 is so bulletproof, you can drive them forever. Which is a good thing as it takes that long to get anywhere."
Betsie: 1984 W123 300D (hobby, 280k miles)
Myrla: 2001 Mazda Protege 2.0 ES 5spd (daily driver, 130k miles)
The Turd: 2007 Toyota Camry (wife's car, 118k miles)