I would either stop with the bottles or just reduce the amount in each bottle. And if he needs it to nap, drop it at mealtimes and offer water instead. Also offer milk after food and not milk before food. If left to his own devices, T would have drank all his calories from milk but we just limited him to small cups at certain times of day.
If you decide to drop the bottle, I really recommend just going to a cup and not a sippy.