Moving 10mo to his cot after Cosleeping

[HoHoHolyMackerel]

Help, please.
DS has coslept with me since birth. I came to the conclusion we're both now keeping each other awake. He seems to feed and suckle all night when I think it is just a case that I am there. Anyway, started moving him two nights ago. Fed, goes down and sleeps exactly two hours, a sleep cycle I know. Then after that it is a vicious fight of wills. Sometimes he goes back down for an hour if I am lucky. Most of the night he will go down for anything like 5-30min before screaming his head off. Problem is I cant comfort him easily as he's on the bottom level of the cot, he's a heavy boy and it is killing my back lifting him in and out.
Ive tried putting him down countless times semi awake but he literally goes mental, it's a no go. I'm sure it's because he's not used to the room iyswim.
This morning my back went out and he ended up back in my bed at 2am 😢
I'm going to try and put him down for a nap today but I also have a 3yo so this is all so much harder second time around!
Does anyone have any advice? I'm exhausted already.

OP, I had each of my DDs in a cot pushed up right next to my side of the bed, with the drop side down so there was no barrier between us. I also used a dummy right from birth, which they used to self settle.
DD1 stayed like that until she was 12 months, when we moved the cot into her own room. We made the room very welcoming with all her favourite teddies etc, and explained it was all hers. She seemed quite happy with that. When she was 15 months I moved her out of the cot to a mattress on the floor “big girl’s bed”, as I was 8 months pregnant and needed the cot free for DD2’s imminent arrival. She was thrilled by that, I think she liked the freedom to get in and out of bed with no bars, and the “grown upness” of it!

I'd suggest a sidecar cot as an interim. This just means removing one side off the cot and butting it up to your bed. It means you can comfort baby while in the cot, then extract yourself afterwards.

Floor bed in his room, made safe. Lie with him then extract yourself. We did this from 14 mo as cot was issue for me too (and no room to sidecar him)