Falling asleep independently

Just wondering how I can encourage my 15 month old son to start falling asleep by himself? He's always had a bottle of milk before bed plus a half bottle before naps, and up until about a month ago he would without fail fall asleep either before the milk ran out or whilst being winded. Now he will do this probably 50% of the time, but the other half he'll tantrum, want to play (and assume that everything you're doing is to try and play too) or an exhausting combination of the two.

I would love to be able to just put him into his crib and let him settle himself and fall asleep, but he just won't- if he's even slightly awake when he's put in there he cries hysterically to the point that be can't breathe and/or throws up, or he'll want to play with something in his room and will try to climb out of the crib to get to it. Either way, I always give in and will take him to my bedroom to lay on the bed and he eventually settled down and falls asleep. When we go to my bed I make sure all of the lights are off, and I don't speak to him or really interact at all, I'm just there to occasionally steer him away from the edge of the bed and then move him into his room again when he's asleep.

I've tried moving/covering his toys (he knows they're there somewhere), giving more milk, burping him more, more naps through the day, less naps through he day, rocking him in his room in the dark, leaving him to cry (although not for too long because I just can't), and more, but he just seems like he can't switch off some nights and then gets so worked up and overtired that nothing helps.

Last night I was feeding him his milk and he was practically asleep, so kept him where he was to let him settle and after 30 seconds or so his eyes sprung open wide, he started laughing and trying to hi-5 me, and then when I shuffled him slightly to try and get him settled again he threw a massive tantrum complete with huge tears and heart-broken sobbing. He's not small either so eventually I had to take him to my bed just out of fear that he would fall off of my lap with all of his wriggling.

I'm aching and exhausted and need some suggestions please!!