yes you can bring water for baby on board. jsut tell them its for babies if they ask. i always do. im not comfortable with water from the crew cos i think they may be tap water or mineral water which i dont think its good for babies. my girl always drinks purified water... so i bring my own. as for ointment n all, i think its ok too. just bring n when they ask, say its for baby.
there are toilets with changing table for baby in the plane. so far all the plane i took has it.
for bottle sterilising.. i dont use bottles so i dont know but then maybe you can ask the stewardess to do it. maybe they will jsut pour hot water into it n then pour away the water...dont think there is microwave or what..