N.O.
What you're pumping is actually a very high volume. Check out this Kellymom link.
http://www.kellymom.com/bf/pumping/pumping_decrease.html
Your supply should be regulating by now. Your body won't make more than your baby needs. That's not a bad thing.
Don't forget that you can never judge if your supply is low by pumping b/c babies are much more efficient than any pump at getting what they need.
Also the rice cereal is very binding. That may be causing him more distress. You can give him avocado as a first food and he'll be fine.
Can they do anything about the anal sphincter? It seems to me that if you have to help him go every time his problem will never get better. Interesting. You've insired me to do some research. I hope he's better soon!