G.H.
it sounds like you are doing the right thing to me.. if he isnt getting enough he would definitely let you know! i have a 16 month old son who gets his main source of nutrition from nursing , he only eats a little bit of baby food daily.. if he isnt getting enough, everyone knows!
from my experience - pumping actually decreases my supply. i only do it if he is really sick and isnt eating or is in the hospital..
the 54th percentile for weight is actually a good place for him to be hanging out! my son is in the 0.02 percentile for weight and i think he is doing great! every child is different, dont let the dr freak you out! i listen to drs all the time quoting by the book, what they dont know though is my child..