This is a situation that is probably going to be more a consult kind of thing. As far as general advice, with ROM I would prioritize doing your best to spend as much time as you can using gravity to extend your knee. This means sitting with your leg up and something under your foot with nothing under your knee. For squats and deadlift, keep adding weight slowly to the bar. You may have to decrease the frequency of load increases to once every couple of weeks and drop the load increases down to 2.5 lbs. Also, this is the type of situation where I have found the knee extension machine to be helpful. If your quad is having trouble coming back online, some isolated knee extension work will force you to challenge it directly. It can also be used as a way to passively force you into greater knee flexion ROMs just by sitting on the machine with some weight on it.
Hope this helps!