You need an A/C unit. 5 or 6 thousand BTU. Only 100 to 175 bucks and most of your problems solved. If you can get one that brings in fresh air that fixes even more. If you just want vents fresh air comes in low to the floor where the air is cool. Vent out from up high to suck the most heat out. If you want it light proof that a little more work. Don't worry about the humidity if you can't get the temp down.
That's alot of plants for 6 feet high room. Do you have the light on a rail system ? What are you growing in ? Hydro ?