His whole schedule just changed drastically. If he's waking to nurse at 2:30am, then by all means nurse him. If he goes back to sleep after eating a full feed, then he needs it and you should feed him.
DO NOT GIVE HIM A BOTTLE OF WATER! At his age, his body is not built to handle all the water and he can actually OD on it. I know you probably aren't giving him an 8oz bottle of water multiple times, but you just never know. Its not recommended and its not a good idea.
I know its getting old fast, but you just have to relax and follow his lead, succumb to the fact that he's just a baby and this too shall pass, and ot give him what he needs now, he will learn that you will always be there and will relax and fall back into a better routine.