1. You should replace all breakers that were potentially submerged. If they were water damaged and corroding, they won't get better with age.
2. It's hard to tell from the pictures you posted, but is the bottom breaker an AC breaker for shore power? If so, a shore power connection should have an ELCI breaker connected within 10' of the shore power inlet, and before anything else. A polarity indicator will likely be part of the new ELCI breaker. However they are bigger than a standard breaker, so fit might be an issue.
3. As mentioned, AC power needs to be kept separate from DC power. Separation can be a simple plexiglass or other non-conductive enclosure around the back of the AC breaker and wiring, so that no contact is possible between conductors. The enclosure can't be removable without the use of tools, per ABYC.
Can anyone tell me if I update my 12v DC accessory control panel if I need to have a reverse polarity switch when using shore power? I cannot find a control panel similar to the one I have to meet my needs. When the main switch is on, there seems to be a loose connection that I cannot access.