If it was me, I would be worried. Not being perfectly level is one thing, but putting torque on a tank is a complete different thing. The stand should be flat, but doesn't need to be perfectly level. The added weight of water is twisting the acrylic in opposite directions.
Will it fail? who knows.... I would tear it down and do it right. A tank (glass or acrylic) should NOT rock on a stand, nor the stand rock on the floor.
Not trying to scare you, but I personally believe this is the biggest reason for tank failures.
Good Luck
Wheat