I think the hospital in STL was mentioned by our cardiac surgeon as being one of the 2 or 3 hospitals (including Vandy Children's) that was the best for pediatric cardiology, so I'm sure your son is in excellent hands.
One of the things that helped me was venting on VN. Seriously. It was cathartic. One of the others was speaking to parents with children who had lived through the same thing that we did.
Seriously...I don't know you from Adam but I'm more than happy to be a sounding board if you need one.