A good stability programme for the knee will include lots of muscle strengthening in a closed chain ie where there is load going through the leg. Slow controlled step downs building up reps to the point of fatigue.

Lots of balance activities

Your knee sounds quite functional so you can push the strengthening quite hard however you should avoid exercises where there are large shear forces through your knee eg heavy weights strapped onto the front of your knee and straightening your knee.

Keep in mind that even with all the good work and no symptoms the instability tests may still be positive because the PCL will not actually shorten. What you want to happen is that the muscle action stabilises the knee actively and that the muscles do not get fatigued too quickly.

Sounds quite achievable form what you have described.