Facing and chasing won't fix this if the threads themselves are misaligned. And using a loose-ball BB might "work" but if the threads are misaligned then it's putting stress on the bearings and spindle that will eventually lead to uneven wear...I'd be surprised if you don't get a little binding with the open BB when properly adjusted. You should make sure of what the problem is, the BB shell might be OK and that Shimano giga pipe might be dodgy in some way...take all of it to your trusty LBS for a check up.