Would you mind also posting your question in the LBG Forum?
If a discovered raider is carried over to the next round does it keep its discovered status?
Do reaction cards (such as non-combatant)played to multiple ship attaks ( like shipping lanes) effect all attacks or just one ship being attacked?
Just one. You may however play a single reaction card for each merchantman. See rule sections 3.3.12 and 3.3.32.