Maybe something to check with the nurse... but I think if he's eating well then that sounds like plenty of milk.
Out of interest do you feel a let-down of milk in those 2 minute feeds? Sometimes P has a very small bfeed but I can tell she's had a few mouthfuls because I feel a letdown. Now that she's getting closer to a year old I like to think of her milk as drinks rather than meals, KWIM? Because she is having 3 meals a day (like your DS) we are not so dependent on the milk for the day's required nutrients. Don't get me wrong, I know milk is still important and there can be too little, but I would think 2 bottles plus a couple of small bfeeds would be sufficient for babies this age... My thoughts for what they're worth anyway!