I know you're probably looking for a proper medical response and all I can give you is some parental experience based on things from my own son but I thought I'd try to respond to a couple of things anyway.
You have said that he has pulmonic insufficiency and that he will be monitored and reviewed in 6 months. Do you mean that his pulmonary valve is insufficient? Did they say anything about this possibly being an existent problem (i.e. that he could have had it for a long time possibly from birth) or did they suggest that this might have occured later. Just wondering because I'd imagine that if it is the first, then given he has already been doing sports with the condition then continuing them (unless of course the specialists suggested otherwise) would probably be fine. If you're really worried though, which understandably you would be, I'd give the specialist a call back (hopefully you were given a contact number) just to clarify this for your own peace of mind.
As far as the rest goes I wouldn't like to say anything that might not be accurate so I'm hoping someone else can help you there.
Keep positive and stay strong
The questions that you are asking are difficult to answer on a forum, it is much better to ask the pediatric cardiologist. I am hoiping that you have seen one? PVC and more commonly, PACs are not genetic; EVERYONE on the face of the earth has them; some people are just ,more prone to noticing them. Premature beats are the 'back-up system for the normal pacemakers in the heart (the SA and VA Nodes). If your son has been seen by a pediatric cardiologist and he has not put any restrictions on your son's activitiesies, you don't have to worry about SCD (sudden cardiac death). If there were even a hint of a problem like that, believe me, he would have ended your son's activities; they don't wait around to see how things are going, they kill it then and there, usually on your first evaluation. SCD is usually a result of something known as Hypertrophic Cardiomyopathy (HCM) which is a muscle disease of the heart. The walls are so thick that they become 'irritable' and that can lead to life threatening arrhythmias which cause the sudden death. As soon as a diagnosis is made, those kids are immediately taken out of sports and their activities are curtailed.