I would love to offer some advice, but unfortunately like Brenda I am from the US and we use different formulas. You might want to ask your dietitian to explain the differences, pros, and cons of each formula. Then base your decision off of that.
As for how MUCH formula he should be drinking that varies from person to person (I figured I would answer this here rather than sending you another message). What one infant drinks could be different from what another infant drinks, because one might be able to eat more protein than the other. As much as I would love to help you that is a question that only his dietitian can answer, because she knows his medical history better such has how much protein he can eat and what his levels have been like.