I need some serious help. if this were your child, what would you do?

some background!

LO is 14 months old. we have never sleep trained him before. he used to STTN from 8:30pm to anywhere from 6am to 8:30am, with maybe the occasional few second long "I can't find my paci" wake ups. he has a bottle before bed and then he falls asleep on my chest in the rocking chair before I place him in bed.

the last 3 nights he has been waking back up at 11:00pm on the dot, and nothing works to get him back to sleep. it took til 12:30 last night.

I can hold him til he is deep asleep, but the second I put him down... he's awake, standing, and screaming before I've even had time to step away from the crib. if I leave the room after this, the screaming will continue to escalate until I go in and pick him back up. seriously, I left him for half an hour the other night, and it just got louder. and then took me another 45 minutes to calm him.

tonight I tried picking him up and calming him, putting him back down and sitting in the floor by his crib as he dozed off. it seemed like the perfect plan! his eyes were drooping and he was staying lying down! however... he proceeded to stay awake with drooping eyes and plentiful yawns for AN HOUR AND A HALF. as long as I stayed still on the floor, he would do everything he could to stay awake. if I dared move (even if he had been perfectly still with eyes mostly shut for 10 min) he would scream.

it's currently 1am and DH is now in there trying his luck. I can hear LO babbling, so I'm thinking it's not going well.

I'm not sure what to do from here. do I assume this is a phase, and wait it out? I know he's not teething right now, because meds don't make a difference. or do I need to try some sort of sleep training? if so, any hints as to what??

I'm convinced CIO won't work. he's got crazy stamina, a serious set of lungs, and I have no backbone. we also have a friend living with us, and I would prefer not to subject him to hours upon hours of screaming every night.

I can't see sitting in the room as he falls asleep working either, based on tonight's experience.

are there other sleep training methods I'm missing? is my addled brain missing something super obvious? if you were me, what would you do now?

ETA: holy novel, batman! if you make it to here without falling asleep, I feel like you deserve some sort of medal!!