Try lowering the game difficulty to the easiest level. That may make it a bit easier. Better to swallow your pride than to restart the whole game.
I honestly think your party is too low level, especially the spell casters. Level 13? You missed a lot of quests, didn't you?
I am at Chap 6 and just finished with Bodhi. My party levels are 20 for my kensai, 18 for Keldorn and Minsc, about 14/14 for Jaheira and Aerie, and 7/14 for Imoen.
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"Butt-kicking for goodness!" - Minsc
"Cities always teem with evil and decay. Let's give it a good shake and SEE WHAT FALLS OUT!!" - Minsc
