No no no no take it easy with him! NO jumping and climbing yet!!!
He needs time. No stairs for a few months, and no jumping for a few months. And NOOOOO running! If you rush it you could injure it more!
Take him swimming! Look online and find a place that will do dog swimming. We have a rehab facility around the corner from us, that is just for dogs. They take the dogs swimming and it makes them use the muscles but in a good way. Usually there is a trainer there that will help you as well. I think they put a life preserver on him and make them swim around for a while. It's very good for them- but you need a controlled environment, like a pool.
We do TONS of acl repairs, and it's a long healing process. Is he not toe touching yet? Just give him a bit of time, and take him swimming. Find that pool. I just looked online and they have tons of hydrotherapy. I highly suggest it. Even if the dog doesn't like it- it's really worth it.
My friend's bulldog had 2 patella surgeries AND a cruciate (acl) done at the same time. She takes him swimming every monday and friday- and he HATES it, but he's doing fantastic since!
Right after the surgery he wouldn't walk at all. Wouldn't take his meds- she went through a REALLY tough time with him. He couldn't go up the stairs for i think 6 months. She still takes him swimming once in a while to keep him strong.