Sleep help for toddler

2.5 (3 in march) has never slept through the night. Wakes 3 to 4 times every. Single. Night. Its exhausting. 

Wake time usually 7-730 nap 3 to 430 bed starts at 8, brush,pee,diaper,book.. then the fight begins. We were laying with him to fall asleep and again everytime he woke up because he flips out screaming and crying till he cant breath. We even got him a full size bed so i wasnt sleeping on the floor anymore. Im literly always exhausted and ended up quiting my job due to so much stress. Dad doesnt help much he sleeps like a rock.

Recent weeks we have tried cutting naps  completely and hes misrible after 6pm and still takes forever to fall asleep. Been trying extinction and walk he back into his room over and over again like 3-4 times a night with him clawing at me to sleep with him sometimes i even hold the door shut and he kicks and screams but eventually he goes back to his bed and falls asleep. But still wakes back up few hours.

I know a late nap is messing with him not being tired to fall asleep

We go back to dr they want to see him for sleep and weight (33 ish lbs but hasnt gained since earily summer) and they suggest melatonin which we have done for 3 months almost and its not helping at all nothing has changed.

Any recommendations aside from running away and leaving the kids behind.. (jk) but really i dont know what else to do.

I also have a 1 year old (turkey baby) who has been sleeping through the night with 1 wake up untill recently about a month hes been sleeping through the night 8pm to 7am.