I think the best thing to do is probably to move them further apart or reduce the amount he takes at each feed, rather than dropping a specific feed.
Could you start by introducing a food-and-drink-and-then-you-can-have-boob policy during the day, so that he takes less at each feed since he will already be fullish. And really really praise him when he has a drink of water or milk or anything that isn't you.

We didn't manage to night wean DS until we stopped co-sleeping though.