There is nothing to be ashamed of to miss a week... sometimes it takes a while to get the hang of this stuff. Major changes!
So just do your best. You're doing great getting yourself back on track!
Having to be careful with my knees right now too, as I pulled my MCL on one side and PCL on the other (yeah, I know- no one does this!) while canyoning.
My doctor says very careful to push through the heels-- never let your knee go in front of the toes. Its all in in sticking the butt out.
In fact... my first round, I did squats in front of a bench-- I would place myself far enough in front that my butt would just barely brush the edge of the bench IF I was doing them correctly. Basically a squat is a sit-down move and this helped me keep my form, make sure I was going down far enough as well as keeping from going on my feet/bending at the ankles.
Another way you can modify is to use an exercise ball on the wall. Don't knock it-- these are harder than they look AND also force the movement to be the proper "sitting" form and protect the knees from over extending.
Trust your body and adjust as needed for YOU! It will work out!