I think it's fantastic that you haven't gained anything back. Very impressive in fact.
Okay, so now it's time to get back to the "losing" aspect of this little journey.
Sounds like you know exactly what needs to be done. Like you said - keeping track, counting points, coming to 3FC. May I also suggest - ridding your home of all the junk and your trigger foods. Adding in some wholesome, nutritious foods. Keeping the bad stuff out and the good stuff in is a great way to get things going again. Plan your meals and snacks so that you know exactly what you are eating so there are no surprises come meal and snack time. So come on girl - let's get to it. Make a commitment to yourself, set up some ground rules and start getting back into the swing of things. Before you know it you will be right back on course. You KNOW you can do this.
As far as the exercise goes, take it nice and slow. Ease into the exercise. Hopefully in a short matter of time those knees will be improving. Swimming, the recumbent bike and the elliptical are all "knee friendly" exercises you might want to try.
Good luck to you. You CAN do this. For sure.