Hi Hugo...glad to hear you got some answers to your pup's problem. Sometimes the not knowing and wondering is worse than the reality.
As everyone has said, your toughest order will be keeping him quiet. Our boy Barkley had a similar issue last year and I found something that helped tremendously was a holistic supplement by Azmira called R&R Essence. It's a combination of herbals in liquid drop form you can give a few times a day that just helps take the edge off. It's not chemical and you can use it longer term if needed. Barkley is a real wild man, and the no running/jumping thing was darn near impossible. Just google Azmira R&R Essence and you can order it online.
For glucosamine, we use Springtime's canine Joint Health Chewables, very cost effective and a great product. You only need to give one a day and they frequently run "buy two, get one free" specials. Again, you can get this online at
www.springtimeinc.com .
Finally, if you don't have good luck with the diet food or want to try one that combines good ingredients in low cal form, I feed Drs. Foster and Smith's diet kibble. Trust me, you will quake if you read the ingredients on those prescription dog foods....very little nutritive value.
I wish you luck with your pup's progress. It sure sounds as if you are on the right track, and good for you for being so on top of things for your little guy!