Transition from formula and bottles

My baby will be 14 months tomorrow. When he turned 12-13 months, we started to give him cows milk mixed with his formula, well it blocked him up like crazy. Pediatrician said to give him benefiber until he gets used to the milk, so that’s fine. Once we got the benefiber we started him back on milk and he’s pooping normally again.

Well now I’m struggling with something else. Now that he’s finally getting used to milk, how do I change his schedule accordingly? He gets a bottle when he wakes up in the morning, at nap time around 12, a small bottle around 4-5, and one again at bedtime. Once he’s drinking milk on its own here very shortly, I plan to take away the bottle. My biggest concern is he won’t sleep well at night. I feel like all his day “bottles” can be substituted with his straw sippy cup of milk and snacks/meals (he’s not the best solid food eater, but I’m sure with enough meals and snacks he’ll be okay without a bottle). But I just don’t see how I’ll be able to put him to bed at night with a sippy cup of milk vs a bottle of formula. Last night was his first night of drinking half formula half milk and he had me up about 4 hours later, and he’s a 10-12 hour sleeper (might have to rock him at most) so I dont know. I just feel at a loss. I feel like he might be able to sleep through the night just on milk from a bottle, but it’ll be tough, let alone trying to get him down while drinking from a straw. Just feel lost trying to do this formula and bottle transition.