"Regarding the loose crank arm. Thoughts? I mean it's really loose. I'm leaning toward removing the crank arm, working on the bottom bracket then....?"
Id guess the cotter is the wrong size and worn from use, Ive come across this a few times. When you get a proper one set it with a hammer and punch as just tightening the nut will not seat/tighten it enough. Some cotters need to be filed to fit correctly. Many people seem to stay away or fear cottered cranks, I never though they are all that bad to work with. Good luck with the 20!