From what you say, you have great inhibition of your r. femoris. A couple of degrees extension lag will not affect your quad. Goniometers are only accurate to+/- 5 deg. Do sustained prone hangs combined with QS and TKE as long as your shin is only 1/2 off the table to prevent hyperextension. Use NMES ( muscle stim ) with your quad exercises to augment muscle recruitment. You can do one leg presses 0-50 deg, walking lunges. The strongest leg will always dominate so use 1 leg
You will have some post-op skin numbness. I wouldn't worry about that.