The good I see.
1. running, Top end recently done
2. Most troubles are minor, good starter project since most things are not too involved.
3. Can be a very reliable bike.
The less good
1. the cb400t is an inherently boring bike. More cheap reliable transportation than 2 wheel excitement.
2. 36 years, is 36 years
A lot of things on his list can just be lived with until you feel like dealing with them. A few should be dealt with for safety reasons.
The sticking throttle should be first. may just need a good cleaning and relube, but more likely it will need new cables.
Petcock. Often cheaper to replace than fix. Old ones screens are usually trash anyway.
Switch gear can likely wait a bit, but if you are taking the throttle apart anyway. Plastic bits may be trash. Original replacements can be hard to find, but swithes off other models can work fine. Sounds like they all need a careful disassembly, cleaning of old grease and likely buffing of contact points. It's rare that I get through something that old with out some plastic parts damaged.
I wouldn't worry about the cosmetics at all. Even new it wasn't a real beauty queen. But then again beauty is in the eye of the beholder.