until a couple of months ago I noticed he wasn't putting weight on the leg so got more xrays and was referred back to the same orthopedist.
non-weight-bearing isn't really a symptom of hip dysplasia; and just because the x-rays show the hip is "terrible" doesn't actually mean the dog is in any pain. I have nothing against surgery, but if a dog is running, jumping, and seems happy I would really question the recommendation for surgery, especially without a trial of joint supplements/ physical therapy/ reducing body weight first (we're talking very thin, not just-not-fat).. Symptoms of hip dysplasia: the dog uses both hind legs at once while running (bunny hop). The dog has a weird "sway" to the walk when observed from behind. Visible wasting of muscles on the affected leg or possible both legs. Difficulty jumping up on things. Difficulty getting up and down from a sit or down. Crooked sits.
I'd be particularly wary of this particular surgeon for performing a TPLO on a dog to "prevent" an ACL tear. That sounds really suspicious to me, it is not something that is usually done.
As to joint supplements- they do work for many people and dogs, despite the lack of scientific evidence. They don't "block pain" they actually help keep the joints in good repair thus no pain is present.