First point of call would be to set your word limit for posts to 250. Focus on writing within that frame and go with a 20% for setting rule. You needn't overload the reader with descriptions, and you can still write dialogue heavy posts whilst describing the action and environment by unveiling it slowly.

I'd be happy to write a thread with you with the above rules and work on it on a post by post basis, if you're willing? It'll be more dynamic and educational that reading a wall of feedback here (from me at least).