Answer: You could reduce to one bottle for a couple of nights, put water in the bottles or stop cold turkey, Either way there’s going to be some protest cries. It’s not so much about how long you need to stay out of his room, but the level of crying he has. If he’s really distressed then you need to go into him more often and offer him comfort with patting and soothing, you could sit on a chair beside his cot and pat him through the cot rails if he’s willing.
It generally takes three nights or so of crying and wakefulness before toddlers learn to go to sleep without the bottles. For the sake of his teeth and his daytime eating and general development you are doing the right thing, he just doesn’t know it.
Offer him a drink of water overnight in case he’s thirsty. Be consistent, calm and work collaboratively with your partner.
It will take a week or more for his daytime appetite to improve, but be patient.
Cheers
Jane