1 1/2in slope over what I'm guessing is 20 ft garage? I personally wouldn't worry about it, why do you need it perfectly level?
I'm curious how was the blow in stuff? I always worried wires and such in the wall might stop it from filling up the cavity below, is it fine enough to not be an issue?
Looks good so far. Any plans for a sink or hose? I know it's a huge time saver in my room. Keep the updates coming.