While we did have weight gain issues with DD, she was well established on solids by 1yo and having plenty of food intake but still had a night feed for a while. Maybe around 16mo? Can't remember now. She didn't consistently sleep through the night until close to 2yo from memory. She's 3.5 now and we still have periods of night waking (obviously we don't still give her a bottle!). DS is 8mo and is waking twice a night for feeds but we have some medical issues we're dealing with which mean he doesn't eat any solids and doesn't have enough formula during the day. It's exhausting but I don't have any expectations for sleeping through any time soon.
Personally I'd just let him have the feed for a few more months and see if he sorts it out himself. All kids are different.