I would suggest the lower leg alignment is the result of the postural tilt. It’s as if he’s cartwheeling instead of rotating. As a result, his hips don’t fully rotate and his center of mass ends up moving to the throwing arm side of the target. Fix the tilt to allow full hip rotation and the lower leg alignment should take care of itself.
I would recommend a couple NPA drills - knee drill and rocker drill - to practice throwing while keeping the head upright and not tilting. Hershiser and cross-over drills would also be good to practice keeping the head and shoulders slightly back while leading with the front hip.