You are definitely doing well in your recovery! I would certainly say that you are on the fast track to recovery. Where you are after 4 months is amazing! The fact that your therapist thinks you need only a couple of more sessions means your leg strength is pretty much back! Of course having that strength back is only half the battle. Now you have to get back to doing the things on it that you want to. There can be some mental hurdles to overcome there that's for sure.
As for your stiffness and discomfort. I am willing to bet that a lot of that is caused by your hardware. And, that really won't get much better until it's removed. It's a night and day difference how your leg feels once that hardware is gone. Every OS has a different opinion about when to remove HW. Some (like my OS) will remove it as early as 6 months, but most seem to prefer to wait until 1 year. Some don't want remove it all unless it's causing problems. I'd talk to your OS about that and would let him know that you do want it out at some point. Talk to anyone who has had theirs removed and almost all of them will tell you they are happy they had it done and that their leg felt much better with it out. Constant dull aches, pain, stiffness, etc all went away once the HW was gone.
Even after the HW is removed it can still be a long while before your leg feels normal again. I am just over 3 years out and can honestly say that my leg didn't feel normal again until just a few months ago. It never really hurt or was uncomfortable, it just felt different. I always compared it to a rusty door. It worked and did everything I wanted it to do but it was always tight. It's only since I started exercising regularly again (riding my exercise bike for 45 minutes 5 days a week) that that tightness went away. I guess for me exercise is to me leg what oil is to that rusty door.
As for kneeling. I wouldn't recommend doing that until at least 6 months at the earliest. A lot of people will tell you not to do that until a year. Reason being the bone is not fully healed and back to 100% until then. Right now that bone is probably at about 80%, which is plenty to do most anything you'd need to do with it in daily activities. Chances of re fracturing it are slim, but it's still a good idea to wait until a year to do high stress activities on it, and kneeling is just that. It places a lot of weight directly on that bone. Also, you probably don't want kneel again until your HW is out. Chances are with that HW in your knee it will hurt or at the least be quite uncomfortable to kneel. Personally I didn't even try to kneel until just over a year after my accident. It was uncomfortable to do even then. I pretty much quite even trying to do it until a couple of months ago. I just figured I could get by without it. Now I can do it easily. I really don't know at what point that could have happened had I tried earlier. Once I started exercising again and that tightness started going away I got a lot more confident in trying things again. Kneeling was one of those things. One day while doing core exercises I just decided to roll over and try it. Sure enough I could do it with ease. But, it feels a little different now. My knee cap rides a bit lower in my leg then it did before my accident (this is fairly common I am told) so it feels different when I kneel. Not painful or uncomfortable, just different. Of course that difference is a constant reminder to me of what happened to my knee. Kneeling is about the last thing to come back with this injury. When you can do it pain free and normally again you pretty much know you have reached the end on that long road to recovery!
Oh, and when you 1st start kneeling again I recommend doing it on soft surfaces. Like on a pillow or bed. If feels ok then you cant try it on harder surfaces, like carpet or the lawn. The last surfaces you should try it on is hardwood flooring, pavement or rock. And then, only if it feels good on the softer surfaces I mentioned above.