hmm i can't answer your ballast/bulb questions, but i can tell you that 78 degrees is a perfect temp. and as for the stale air thing, if you have fans blowing around in the room along with an outtake- it should be totally fine. that's actually what i have going on in my closet grow right now- an outtake but no intake. just rebuilt the room recently and the temps have been low so havent bothered to put the intake fans back together agian. anyways, you should be fine.