A 3/4 inch per foot slope on a container roof is overkill and you just made the wind problem worse. Tucson gets those 60 mph gusts during monsoon season, and now you've got a big sail sitting up there catching every bit of it. That extra 2x6 lift also means the low side edge is now higher than your door frame, so water that sheets off is going to splash back against the wall and rust it from the outside instead. A 1/4 inch slope drains fine if you just fix the low spots with some self leveling compound or a patch panel instead of jacking the whole thing.