PFS is generally caused by the patella tracking laterally. Your coach was partially right in steering you to the knee extension. I would go further and say the the knee extension, last 30degrees of that movement only. You also need to look at the hip and ankle as well. for the hip you want to see if the lateral, outside of the thigh, aspect of the hip is tight. If that is the case you want to strengthen the medial, inner thigh, aspect of the thigh and increase your flexibility on the outside of the thigh.
For the ankle sprain you definetly want to regain strength in that ankle. Some ankle movements would be great, calf raises, plantar flexion exercises, as well as the oposite movment, dorsi flexion.
The knee is a problem when you are "running around or tossing" because of strength discrepancies between your medial thigh and lateral thigh. Yes, you can narrow it down to VMO but your body is a system of muscles that orchestrate movement.
Hope this helps!