How do I get my 16mth old on a better sleep schedule?

He’s never required a lot of sleep and only takes 1 nap a day (if that) and he’ll sleep anywhere from 5mins-45mins. But once he wakes up, he’s up. A lot of the time he doesn’t nap at all though. Ive been trying to get him on a better sleep schedule and im really having a hard time. He goes to bed about 4:30am-6:30am!!! and then sleeps until 3:00ish pm! If I put him to bed any earlier he will just cry and scream and stand up at the head of the crib and then fall onto his hands and crawl to the foot of the bed and then stand up and then turn around and fall onto his hands and crawl back to the head of the crib laughing but on the verge of crying. He will do this over and over if I’m in the room. And If I leave the room, he just cries and screams constantly. He doesn’t eventually fall asleep. He will cry until I come back in the room or until I take him out of his crib. Ive tried for 2 hours to get him to sleep. Its like his body is on a timer and he knows it’s not 4:30 yet. And in the days I try to get him in bed earlier, he always ends up finally falling asleep 1-2 hours later than 4:30! So there’s no point and im accomplishing nothing. He eats at 3:30, 8:00, 12:30 and then a cereal bottle right before bed. The cereal bottle does help him to go to sleep on time at 4:30am, at least for most days. This sleep schedule makes life very difficult tho. I feel like I’ve tried everything so I figured I’d ask what you would suggest.

also is the 5,10,15 min rule a good or bad thing to do? When he cries, let him cry for 5 mins, then check on him and then if he’s all good,(maybe give him a small bottle) say goodnight again and leave for 10mins. If he’s still crying, do a repeat check and leave again for 15mins. I do do that, so im wondering if it’s bad? I have a hard time just letting him cry for a longggg time, and he doesn’t “ tire himself out and eventually fall asleep”. He used to stay up until 6:30am to go to bed always, but I was able to work him (very slowly) to 4:30am now for the most part but it’s just not good enough. And it’s like he won’t budge now and go to bed ANY earlier.

thanks for any advice you can give.