having trouble at the end

Hi everyone. I have been a lurker but this is my first post. I have been having trouble finishing the end(s) I did not really struggle with most of the game but I am to the last battle and also to the shipwreck level 4 in Balduran and past the Chess game in Durlags tower. Do I have the wrong characters? I have a Berserker, Minsc, Branwen, and Kivan all level 8 and Xan and Imoen at level 9. Or perhaps I just am not using the right spells? I tried to google good spells for Xan but did not find much.

I know I am late to the party lol, but any advice would be greatly appreciated.