I'll answer some questions.
8. Your first goal should be to get a five star card and then to get enough cards that you can field 3 stars for the rest. You aren't seriously competitive until you can do that unfortunately.

11. You can just not party with him but heal him as he's doing overworld stuff. That way he gets exp (incidentally, thats the best way to lvl blu)

12. All mounts fly now.

13. Only your personal chocobo is customizeable. You can turn it black, but it takes some rng to do so. Look up chocobo color change and there should be a site that tells you what to feed and what order. But once again, some rng is involved.

Fisher plays completely different than miner/botanist. It tends to only be relevant in a few culinarian and alchemist recipes, otherwise you just fish for the enjoyment of it/certain minionstdisplaying fish in your house. This is deliberate