I have a 16 month old daughter who does not take a bottle during the day, but eats three meals plus 2 snacks a day. She has been sleeping through the night since she was 5 months old, and will sleep 12 hours a night - at times, she wakes up for whatever reason, and cant get back to sleep with just rocking or patting, I will give her a bottle. Its a soothing thing - and it really has nothing to do with the milk itself. It is not uncommon, and perfectly normal and healthy for a child to still need the nighttime bottle until they are 18 months old.
But, as a child psychologist, this is what I tell me clients who want to get their babies off the bottle: start diluting his milk with water, increasing the amount of water over a week or two until the bottle is mostly all water, and now undesireable. He should then give up the bottle easily - does he have a "lovie" like a special blanket, stuffed animal, even a binky (also healthy for a child to use at night until about 2) to take the place of the bottle? If he does not, start introducing something like a blankie or animal for him to cuddle up with. If you want him to wean from the bottle at night, you have to replace his need for comfort with another object so that he does not feel abandoned. When you take both bottle and the smell and comfort of Mommys arms away with nothing to replace it with, a childs sleeping schedule can become extremely difficult.
Don't feel bad about not taking the bottle away yet, you haven't done anything to harm him!