Great job on this little guy, Corinne. You figured out the problem behind most of his ailments, so there is actually only one left to solve.
Both patellar luxation and the nasal congestion are commonly associated with a tendency Wind invasion. Wind invasion of the dorsum causes spinal stiffness and fixations that then interfere with his own ability to keep his patellas inline using his glutes. A chiropractic evaluation might help a lot to restore that ability.
To help preserve any benefits of a chiropractic treatment (or to improve him slowly if those services aren't available), we need to probably choose a Wind expelling formula, which means choosing the type of Wind that is invading him. You can't be invaded by something unless you're prone to it already. In his case, that is Dampness. So we are looking for a Wind Damp formula that helps with the nose and back.
San Ren Tang actually fits that bill, so you could just start there. I don't think BH&K is a bad idea either.
If his nasal congestion improves, but nothing else, then I would look at Yi Yi Ren Tang next. It's one of my go-tos for patellar luxation
Hopefully this helps you out! I think you're right on track. If not, then we can both be wrong together!
Steve