I thought about that but I can't really get to the back side since its against the wall
Maybe I'm dense. (Trust me, a lot of people don't think it's a "maybe"...) But, I can't tell from the thread what is not level. Is it the floor, the carpet, the stand or the tank? The solution depends on which one is causing the problem.
I've placed large tanks on carpet (everything from a 55 and 75 to a 180) without a problem. As long as the floor is strong enough and you protect the carpet it's fine.
However, I agree with everyone that filling and using a tank that is off by so much is courting disaster. There is really no option in my mind to using that until the problem is properly resolved. And yes, no water should be in the tank (and preferably no substrate) until it's all fixed.