I finally got some time to work on this project again. Picked up where I left off and got 2s and 3s charging tested. It is now automatically charging and balancing 2s, 3s, and 4s batteries!

I set my bench supply to 20V and was able to get it to charge a 4s battery at 45W! It was also balancing and the temperature of the MCU did rise to 44C at room temperature. So heat may be an issue in the future.