A trip back to his physician to re-evaluate his situation might be a good idea. Also working with a PT could help you get a better idea of how to proceed next with your client. The PT could provide you with some extra suggestions to help you design a better and more effective strength program for him.
I am trying to picture your assessment of 50 % rectus femoris ROM but I am struggling with that. Can you re-phrase this question maybe with reference of knee and hip flexion and extension.
Regardless of your answer to that, it appears that this client perceives a deficit in range of motion. I would recommend to this client that he be assessed by a physical therapist. Chances are that there is a significant amount of scar tissue which cannot just be stretched away.