heat issue

hey all i dont have a camera yet, so i cant post pictures. im cutting my 7x4x10 ft closet in half and having some heat issues when i run my light. i tested it last night and this morning after 12 hours my room went from 78-80 degrees to 90-93 degrees as far as possible from the light hood, and about 100 degrees a foot and a half below the hood itself. i have a 6 inch fan and a 6 inch hood for my 600w hps. my first problem is i already have a 4inch hole cut for exhaust so i have a 6-4 " reducer on the dryer vent going out the wall. my second issue is im already Extremely limited on space as im using 4 feet for the flowering room and 3 feet for my vegging/mother, and using the 6-4 reducer makes it so my 6" venting is bent not getting full air flow. i want to increase my hole to 6 inches but the wall is thick stucco and i already have a 4" cut so i have no pilot. Any ideas on what i can do to increase my hole to 6". Also where could i get a 6" dryer vent so i wont have bugs and shit trying to crawl in when the fans not running.