Hi
Sorry to hear about all your issues. Isolated VMO training has been shown to not be possible according to recent research. I will try and find the articles. I have them in the pile upstairs somewhere. Sometimes I wish physicians would leave the rehabilitation to those who actually studied it for several years, and not a few hours (Sorry off my soap box now). General quadriceps strengthening is usually performed. For example quadsetting, straight leg raises etc. There are a myriad of them.
Part of the problem with multiple dislocations is the loss of or laxity of medial restraints that help hold the patella centered. The quadriceps muscles have a general lateral pull and without medial restraints it is hard to stop lateral dislocation.
One of the key things I do with pts is teach them how to control the knee during activities. A knee that collapses inwards under load can increase the chances of lateral dislocation. I am sure to have pts learn motor control, look at the hip for weak hip muscles causing the femur to internally rotate, and also at the ankle for excessive pronation, which all can contribute to medial collapse.

Hope that helps
KiwiDPT