Your son seems pretty good considering his experience. Did he start learning the axel ?
However it seems a little soon to spend a lot of money traveling for ISI competitions, considering the choice you have to face money wise. He can still test and when he gets to USFSA categories and improve, you will see then if he can have competitive potential.
If it happens that your son doesn't improve (like he he can't do double jumps), maybe it still can be interesting, if he likes it, to compete even at a lower level.
Fun and challenge is not made only for high level competitors.
But maybe for now you still have a little time to see how far his potential can lead him. If it happens that your son can reach a good competitive level, you will have plenty of occasions to see how much competitions cost ! lol