You are never going to get this specific bike looking good without a ton of parts and work. It's just so obviously clapped out. Replacement seems much more reasonable. All the functionally identical replacements are also unfortunately the same thirty years old, but maybe they didn't spend so much time out in the yard, you hope. What are you seeing right now when you look on Marketplace or Craigslist?

the key things you would be looking for are
your size
the words "chromoly" and even better, "butted" on the frame decals
silvery alloy parts (like your brake calipers) not rusty painted steel (like your handlebars / stem)
not clapped out