I agree on the weight. You want to keep him lean and build those back leg muscles a little more. But the wiggle....well I had an OFA good dog whose but moved around like that when he walked. In the end, he did have lower back issues. We are planning on going to a sports medicine DVM for an assessment this summer for a good exercise plan even though we don't have any known issues.
They have physical therapy vets for dogs and that would be a great place for a consult and a plan for appropriate exercise for yours. [though they may try to see you on their hydrotherapy sessions, which I just said I could not do, but the plan helped me keep mine in good shape and her HD was severe]
Walking uphill is very good, going from sit to a stand, walking in chest high water, to keep him in good shape. The more you can to to keep the back leg muscles strong, the more support for the hip joint, and the less arthritis.
You can add green beans. 32 oz if you are using a measuring cup seems a lot for a dog that is only walking 2 miles a day. But go on weight. He is too heavy so needs to eat less.
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