I need help with 4 remake

I am sorry if it is obvious, but i have OCD caused concentration issues.

1. What weapons should I buy, upgrade and carry. I am at the sea monster boss fight right now.
2. Will there be ways to expand my inventory since i always run out of place since i barely am able to Stock kinds of items.
3. Can i lock myself out of progress like have no ammo or is there a system to always drop ammo when you are about to run out. FYI i play easy/assistant mode.
4. Whats the best way to defeat the different enemy types?
5. Is there a map to buy to know if you collected everything in an area?