For torn rotator cuff (15mph motorcycle incident, pain, can't lift arm) 1-should i sling or use as possible (w/w'out pain), 2-should i lift arm with other hand to maintain range of motion (until medicaid assistance is approved to seek med attention)?

Typically you can sling for comfort and take tylenol/ibuprofen if you can tolerate for pain. But you should as well try to maintain some range of motion at least a few times per day. The best way to do this is lean forward and dangling you arm like an elephant trunk and then while dangling do circular motions with your hand. Once it becomes less painful, you can work on more ROM with other hand.