my suggestion is to leave it at 92 (that's really not too high) actually it might make them grow better, since the molecules move faster in higher temps...then, since you're height restricted...SCROG it! Primeralives SCROG setup and grow (coments welcome)
read some of the posts, they'll explain how it works in it..really efficient! and for heat, maybe return that 400w, and (maybe) get a 400w with an air duct...High Tech Garden Supply ! that reflector also has the glass shield on it, so the fan in it won't blow away your CO2! hope that helps!