Hello :)
1. Yes, in my discord there's a pinned Google Sheet with all the cards, their effects and the mechanics.
2. It can be, although they may grow faster than you. Good if you need to unlock CG's for a specific character.
3. Same as answer 1.
4. Most will be 5 positive interactions, some will be 7.
5. One answer is a positive in relationship, one is negative and one is neutral.
6. Some characters can not be allies. Only the ones that appear from the start. The characters that join halfway through cannot be made into allies.