I am not sure what might help, but here is one idea. Some people see doing form as an exercise in aligning bones and hard tissue with a minimum of exertion. I think that this can be misleading and can lead to the stagnation of letting the qi dictate your [/yi] ("mind intent"). Let me explain.
A better way to view doing form may be as an exercise in aligning soft tissue, in which the hard tissues are mere connectors of soft tissue. Imagine that your body is like that of an octopus. You can walk, stand, push, and pull as you want, but you must actively form your "attachments" and "connections" with the ground. Even if you only do this passively or unconsciously, your passive mind intent will dictate your alignment. Your hard structures are not stable by themselves. If you are unconscious and unable to express any mind intent, the energy of your body structure will be completely unorganized even though your soft tissues may be complete "relaxed."
It is customary to think of the sole of the foot as a given and to think that how your sole rolls onto the ground will dictate your knee alignment. I am suggesting that you not focus on the external structure, but on the energy relationship you are trying to establish. Your knees can only deviate to the side if you feel that the alignment of your lower leg dictates the movement of your knee. Instead, feel that you are an octopus and that the energy expressed through your leg-like "tentacle" requires active shaping by your mind. You must actively dictate how the muscles in your sole interact with the ground and how the tendons in your knee decide to extend and contract. The shape of your "hard" tissues will be a factor in how you decide to control your soft tissues, but they do not dictate the outcome.
To get a feel for this, stand in Wuji/Wu Chi posture with your feet parallel and shoulder width apart. Without moving your feet more than a quarter inch, try to move them apart so that the outside edges dig into the ground. Feel what effect this has on your knees. Now try to move them together so that the inside edges dig into the ground. Feel what effect this has on your knees. The two sensations should be dramatically different, and neither is controlled by the shape of your leg bones, the sole of your feet, or your insteps. As you do form, realize that you must focus on the same type of control, except that most of the time you want to have the feeling of energy traveling straight up through your legs. In fact, the back leg is often thrusting into the ground, while the front leg is applying a counter propping up force. These forces should travel in perfect straight lines and/or circles irrespective of the shape of your actual anatomy.
One way to begin to train this approach is actually to put more energy into your legs than normal, so that the feeling of using your tendons and muscles is always clear and that you always have a distinct bodily sensation to modulate. Since you are actively using your knees to do something, you will instinctively not do something that weakens, threatens, or exhausts them. If, on the other hand, you try to empty all feeling of energy and exertion from your tendons and muscles, it is easy to begin letting external structure dictate internal structure. If your external structure is naturally less than optimal, you may inadvertently exaggerate whatever problems you have as you train the defiency into how you use your body.
I hope this helps.