Welcome and don't lose heart. These are older bikes and do require TLC. I have an '85 Limited Edition fuel injected model and it is a challenge at times. You will be able to get the bike to a good standard mechanically, timing belts, tires, brakes, bearings and the likes. The carbs may need to be done, but this is a one time issue (hopefully). I have been rebuilding mine for the past five years and what I find works is to determine what I want to achieve in a work/maintenance periods of say three weeks or less. Do this, then ride for a while. Contemplate the next work/maintenance period, determine what you to do and when. I try to always do what I set out to do, then ride again. Do not go down the rabbit hole so to speak. Easy to say I can do that now, do this only if it is necessary for personal and road safety. Put the issue into the next work period. You will be wrenching, but you can find a balance between wrenching and riding.
I would also recommend to remove/disconnect any additions to the bike from the OEM system wiring. The bike's electrical system is designed to the minimum standard necessary to safely operate the bike as it came from the factory. I would install an accessory fuse block that integrates ground and power. Doing this will ensure that you can troubleshoot quickly, and you're not guessing whether it is the OEM side of the equation, or the additions. Always good to have a known starting point.
When I want to do work on the '85 1200, I look at the weather channel as well. Better to wrench when it's raining than when it's not.
No quick fixes with an older bike, but it'll get better with each work/maintenance period done. Good luck