There is a PCD Foundation website. They had a forum at one time, but now have a closed facebook group you can join. I would encourage you to contact one of the consortium clinics (PCD clinics) to discuss the information you have at this time. I have 2 recessive genes and my organs are on the correct side, so I was never diagnosed. There are 5 main PCD genes, but the consortium in mapping out genetic information and will probably have a growing number of mutations over time. Treatment is to follow CF protocol to prevent lung damage.
Not sure if your child is too young, but a nasal nitric oxide test provides clear evidence of PCD. It is low for CF and very low for PCD. Easy and quick, but not a lot of places have the equipment.
Also, if your son is getting pneumonia frequently, you may want to look into CPT (manual percussion therapy) or a vest (ask doctor) to loosen and clear mucus. As a child, my mom thumped my chest while I hung over the couch. A vest device is much easier, but insurance will want a diagnosis to cover. Sometimes just gathering pieces of evidence can get coverage - bronchiectasis, hospitalizations, etc