Trust me, skinned-kid teenagers make Jack seem like a walk in the park. If Jack stopped listening to you, put him back on the leash and go back to basics. Sometimes I've had to do a little remedial training with Merlin too. Even a five minute session of sit/stay in the middle of a liesurely walk daily for a week can get the habit back of planting that rump before they have a chance to think---I don't wanna. Also, make him sit before anything good happens--walks, feeding (which you do), play sessions,potty trips outside, and attention from you. It reinforces that good things happen when I lisen and sit. Just some suggestions for you.
Stella-currently surviving life with a 17 year old and 11 year old skin-kids