hi. i would stick with the night feed, he's probably hungrey at this age, i imagine althought he's having 3 meals it's only a small amount so he's probably not full enough through the night. start weaning him off night feed at 6mths, thats when they start waking through habit/comfort and start normally to wake more often for milk. but you shouldn't simply give water instead, wean him off, half an ounce less each night until he gets to his last half ounce feed, that'l be his last night feed,(alot of fathing i know but worth it) the next night if he wakes stick to water but you have to not give in and go back to milk! he'll get used to it at that age and except it better than trying to struggle with him now when he's not ready. after that he should start to sleep better again. don't listen to anyone, your child is very different to your friends, they don't know your child, you'll know best when the time comes.
