Toddlers sleep schedule - 15mo old

I posted earlier last week but I’m back 😖 My 15mo old is waking in the middle of the night, crying. Which then turns into screaming. Sometimes he’s throws up he gets so upset (this isn’t out of the norm, done this since he was an infant) I’m really very unsure what the issue is and need a place to start to cross one off. Somethings I’m considering are teething - which he is definitely getting in his top molars. One has popped through, the other is JUST about to. He’s also at the tail end of a major leap.. two more days until the end of it. 3, he’s such a picky eater and doesn’t eat a lot, even if I feed him “on the go” per say. I remember the pediatrician telling me “some days you’ll feel like he ate nothing, and some days he won’t stop eating.. he will survive. It might feel like they’re surviving off air but toddlers are a mystery” so at bedtime I add two scoops of toddler next step to give him that extra nutrition for the night. 🤷🏼‍♀️ 4, is he having separation anxiety? I don’t notice any of the telltale signs and before I read how to calm him back to sleep I would try to snuggle him in bed to get him back to sleep and he isn’t having it... don’t really think that’s it. 5, night terrors? Not sure. When he “wakes up” he actually wakes up. Eyes are open, and it’s usually him waking up my moving or something not jolting awake that I’ve noticed. When I go in, I rub his back for a minute and lay my hand there until he’s calm for about 4 mins give or take, then walk out. He begins to scream! I do it 3 times then he cries it out. I’m just wondering is it time to start letting him fall asleep on his own in his crib... I’ve rocked him since he was an infant... opinions, help ?! Even though he’s exhausting, I still love his little face 😍♥️