I am in a 800sqft space with 20ft ceilings and a 3 ton HVAC unit that now seems to run 24/7.
Holy shit dude...you could be fighting like, 30,000watts with that unit. You just need an exhaust solution, not a 3 ton compressor.
Hum, no. 1 ton of cooling is 3517 Watt. So a 3-ton HVAC can cool about 10.6kW of equipment, or a bit more assuming heat loss in the server room.
Some use no HVAC to cool 10.6kW of equipment, but that's a completely different DC cooling strategy

Yes, and to fight watt for watt is moronic when simple flowthrough can handle the issue. Why run a huge compressor with your fans if the fans themselves can be sufficient? See smoked_out's post. Another option to increase efficiency would be to cool a small space with AC and draw air from the space, through the room, and out the exhaust. Look up the concept of a 'lung' for cooling indoor grows.