DS is an awesome sleeper. I think he was always going to be a pretty good sleeper, but I'd like to take a little credit for making a good sleeper into an awesome one! I know you've probably heard it before, but I found consistency is the key. You really need to stick with, and believe in, whatever method you choose. We decided DS wasn't going to co-sleep, and he never has (just our choice, no judgement for anyone else). The very few nights we've been up with him, we've spent on the lounge, or on the floor of his room. We decided we weren't going to do CC, though we also decided not to rush straight in and pick him up the moment he cries. From about 7-8 months, we decided we weren't going to pick him up every time we went in (my back just couldn't handle it). We'd give him a minute or so to see if he self-settled, and if he still needed us, we'd go in. We also got to know his cries/sounds and wouldn't go in for grizzling (I find DS needs to make a bit of a grizzle type sound before he goes to sleep, a kind of moan, and he still does quite often now. It's part of his settling routine). We'd cuddle him if he was really upset, or otherwise just pat him until he settled. Then we'd pat the mattress, the whole time saying 'shhhh' or something else repetitive and soothing. Gradually the patting would get slower, until it was no patting, just the 'shhhhh's. We started patting to sleep, then gradually left just before he was asleep, then a little earlier each time. It took a good few weeks, and we'd sometimes have to go back and resettle. Because he was going to sleep on his own, it meant he could go BACK to sleep on his own if he woke up in the night. I remember getting up in the night to go to him because he'd cried out, only to get to his room and he'd be fast asleep again! It's only been in the last couple of months that I've been able to stop myself getting up 'just to check' every time he makes a peep. Nowadays, he'll tell me when he's ready for bed, and points to the door, telling us to go after we've put him in his cot!
I'm not sure any of this advice will help - it's got to be something you're willing to invest in and be consistent with. The moment you give in and say 'oh it's easier if I just pick him up/put him in bed with me/feed to sleep etc', then you start again. And if it IS easier for you to do those things, then do them. For me, it wasn't easier, because I knew I'd be doing them multiple times a night, night after night, day after day and I didn't want that. I also had a friend whose 8 yo and 4 yo were still getting in bed with them after midnight most nights, and would wake up several times a night before midnight and the thought of that petrified me! Oh, and I'm a teacher, so the whole self-discipline thing (me being self-disciplined, not DS) isn't that hard. I know the motto 'Certainty, not severity' too so I just knew that DS needed to be certain the same thing would happen time after time after time. The last thing is that DH was always very supportive and consistent with what we did too and was always more than willing to share the load. That makes a huge difference.
I really feel for you. Sleep deprivation is HARD and x3 must be an absolute nightmare for you. I hope you find something that works for you soon. Look after yourself because without you, your LO's would be lost. Having you healthy and happy is what is best for them.