Dear friend, welcome to HCM!
I think you are correct.
A PFO may remain asymptomatic for long.
But his symptoms are definitely cardiac and may be due to worsening of shunt through PFO.
and warrants urgent evaluation.
Does he turn bluish when symptomatic? Cyanosis
(bluish tongue, fingers, earlobes etc) indicate low oxygenation with reversal of shunt across PFO.
When was the last 2D echo done?
A doppler/ echo will definitely pick up complications of PFO and ASD with reversing shunt.
If you feel, may take a second opinion
and go to a good tertiary care haert centre / university hospital with paediatric cardiac surgical facility.
Get labs, echo/doppler and ECG done and seek paediatric cardiology consult.
Do not neglect.
Take care and please keep me informed of your progress.
I hope to have answered your query satisfactorily.