Seems like you realize what you need to work on without people telling you, which is good. I'm not very experienced with coaching but let me try to help anyways, and someone better like CoachJim or cgeorg can correct me if I'm way off.
For your bent elbow, I don't really see what you mean. If you mean after releasing the ball, I don't think it's a big problem. If you think it's affecting you(and it might because you may just be doing it too much), you can try actually reaching out to your target to get the feel of coming through the ball instead of up. But even most of the pros bend in the follow through.
Again, even the pros tilt in the direction of their bowling arm. Look at Jason Couch, Tommy Jones, Chris Barnes, the list goes on. But at the same time, not everyone is the same. So if you feel it's hurting your game, you can focus on keeping your head above your sliding foot and that's the ideal finishing position.
As for your footwork, your first two steps are fine but after that you are rushing it a bit. Try to keep your steps a little more fluid. Your slide step is also bigger than all your other steps from what I could see, but I'm not sure whether or not that's a problem. Also, ome shots your throw your trail leg a little far to the left and in the air. Try to keep it lower and more inside, that way your hips don't open any more than they need to at the line.
I'm completely lost on your pinkie finger problem. I think you lose leverage and/or revs if your pinkie is not in contact with the ball. I'll let someone else figure that one out though.