MarnaLou --
Not out of the woods, but how wonderful to have some new ideas to try for Stewart. Good behavioralists amaze me a bit with their insights, and I hope for you this adjusted approach works out. Seems to me you have real reason for optimism.
By the way, I wouldn't have thought of a muzzle either, but if that is what it takes to get Stewart the exercise he needs it sounds like a good idea. Obviously Stewart will be happier getting the exercise and play he needs.
All the best, and do keep us posted.