HI, I'm not a biological mum, but i have spent 17 yrs working with kids and to be honest, i think it may be worth a try of incresing his oz's and seeing if that helps. Have you tried colic drops? Give baby warm boiled water inbetween feeds?
I think its a case of trying what YOU feel is best for YOUR baby - because at the end of the day, you know your own child better. Just try everything that is reccommended by your healthvisitor and if in ANY doubt, see your GP.
Good luck and give baby big hugs from the A&B family hehehehe