I'm in the same boat with our Chow/Rot mix. Draco has a deformed hip joint and cannot run, sorta trots and can walk for about a half mile before he's done. He weighs in around 110 lbs and vet said he needs to loose 20 lbs.
We have cut back his food, no table food and very few treats and no weight loss.
I do get him out nightly to walk the property but he is unable to go for too long. He is now four years old so not sure how more years of quality life to expect. Ask the vet about amputation but he said it's a no go.
Draco will get lots of love and attention and enjoy as many camping trips as possible.
Good luck with your fur baby, I hope you find a solutuon.