Jaw Botox for unsymmetrical jaw- how many units for slimming on one side? (photos)

I have a very small head/face and due to my bite/teeth being dominant on one side, my jaw one only one side has grown very large. I am interested in massater botox to fix before my wedding but have already lost facial fat causing cheek wrinkles, so ideally only want to slim the larger side a little. How many units recommended for each side? Dr said it’s too risky to do only 1 side but I don’t want to lose more volume on my small side as it already has a little sag due to fat loss. Thank you!