Hi,

I think 85 will do, try to keep the door open as much as possible, but once it doesn't go much higher than 85 it should be fine. The only way I can think of reducing the temp is to somehow get cool air from outside or exhaust the warm air to somewhere else.

Even though 85 is fine, you might have high humidity levels. It's fine throughout vegging but for the last couple of weeks of flowering you might want to keep humidity under 40% to stop mould growing on your buds if they are really thick.

All I can suggest is leaving the door open as often as you can or finding a way to get fresh air into your room. A dehumidifier or air conditioner would work but it really isn't worth it for a small grow space. Try it out and see how it goes. In my opinion your only real problem is the high humidity for the last couple of weeks of flowering.70-80% humidity and temps of 80-85 shouldn't be a problem the rest of the time.