I would try the Yahoo group disabledrabbits . Their members have a lot of experience with bunnies that need help getting around. Another one that may be good is etherbun , also on Yahoo. Bunnies with splayed legs can live fine, but the fact that his back legs seem to be getting worse is not encouraging. A single leg splayed usually is no problem, but more than one can put unusual pressure on the organs that can cause them to fail.
We had a member with two young buns that were severely splayed (named Holiday and Fiesta), and she kept them in a baby pool with absorbent material underneath polarfleece. The polarfleece wicks away moisture and the absorbent material helps keep them dry. Artificial sheepskin can also wick moisture away well.
X-rays would be useful, I agree. It is possible that the bones are growing abnormally and it is causing pain. I would definitely have him seen by a vet, the nearest vet school if you can. It is not a terribly common thing to see so a more expert opinion may be helpful.
I would also contact the breeder if possible and tell them that he has splay leg--that is something that the breeder would want to know in order to keep it out of their lines. The parents probably should not be bred together again, etc.
You can search for Holiday and Fiesta to see some good threads on severe splay. The member who had them was Leaf, I think. Also, here is our Library thread on splay leg with links to many good sites:
http://www.rabbitsonline.net/view_topic.php?id=54150&forum_id=10 . Another member who has a lot of experience with disabled bunnies is TreasuredFriend. She usually responds to PMs but is not often on otherwise. She has had at least one bunny with hind leg mobility issues. A lot of members have had bunnies with one "wonky" leg, whether it was splay or a break that did not heal properly, but I don't think that this is the same kind of thing.