Hey fellow Dan!
First question is who made the armor? It looks like a Jim Tripon fiberglass kit.
I'll try to answer the topics I had to deal with my build:
1. If you aren't going for L2, you should be able to use a dremel and shave down the visor for a better fit.
4. The belt can be remade if you buy the rubber matting and follow the Jolly Roger's belt guide, but many people are now building them where the overlap is in front, covered by one of the two pouches on the side of the buckle. It's for easier suiting up.
6. Are these Doc Marten's or Crowprops shoes? Maybe you can take it to a shoe repair shop? Also, the ribbed flap covering the laces should go under the shin armor.
Biggest advice is to start small with your updates, with what you are comfortable doing. See if your local garrison has people that can help out as well. It will give you good practice in maintaining/fixing future armor issues.