Both of those issues lead to one question. How tightly are you holding the violin and the bow. I’m new to this forum but I’m sure it’s been pointed out here that you supporting the violin with your neck and shoulder. This leaves your hand looser to move more freely in positions and for vibrato. It also makes it harder for your hand to cramp. A bouncing bow is many times the same issue. You need a relaxed bow hold and a loose wrist to bow properly. For some reason the bouncing bow usually happens on the down rather than the up bow for most people.it could also be a bow thats not well balanced. Better bows track better and are easier to play.