One thing you have to always remeber when it comes to orthopedics is patience and that it takes time, physcial therapy is great and needs to be done, but you want to do it gradually, for example today let him walk on it for about 10-15 mins then let him rest. Then each day gradually increase the time.
Also if you are not going to be with him all day everyday, then you should reconsider doing this at home. A therapist would be a better option, and they will do a different type of therapy. Alot are now doing hydrotherapy.
The limping is normal, but over time he will start putting weight on that leg.
Please let me know if you have any questions.