Answers...in the order questions were received...
1. The invasion quest at the keep definetely does happen, no matter what else you do in the game. It may take a while, but don't worry - you'll fend off invaders soon enough.
2. I assume you mean Dermin. No, the Jaheira romance does not stop here. You will be visited soon by a familar face.
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a bunch of long hairs.
trux