Poor you and I am very sympathetic. I don't think, though, that it is fair on a child to go from feeding to sleep to controlled crying in one night. That is a big shock and the child is bound to be upset, confused and angry. I know this sounds very harsh when you are exhausted - but it is really cruel to go from co-sleeping, bf during the night, bf to sleep to controlled crying in your own room in ONE night! It's an awful way to do it. I know you're exhausted, but you need to accept that this needs to be a gradual process - it will probably take 2-3 months to go from fed-to-sleep, fed-during-night, co-sleeping child to a go-to-sleep-on-own-in-own-room-and-sleep-through-the-night child. In fact, with mine, the process took longer, but i think it could have been sped up if I'd wanted - but not to one night!
I think you need to plan by stages. I talk from experience having only just (1 week ago) stopped feeding my nearly 3yo DD to sleep. She is also my third child so have been through this before. Each time it feels impossible, but somehow it happens. And it happens by stages.
I think the way to do it is to pick one behaviour at a time to change.
I would recommend starting with the 'feeding at night'. Continue to feed to sleep, but when he wakes in the night, only offer water. He will get cross at first, and you will have some pretty sleepless nights, but he will accept it in the end - and he still has you there for comfort. The important thing - talk about what's going to happen before it does.
When that is established, the next step could be 'starting the night in your own bed'. Continue to feed to sleep, but put him in his bed rather than yours. When he wakes in the night, let him come into your bed.
Once that's established, the next step is to stop feeding to sleep. With my DD (also a very strong-minded child) I did it this way:- For a couple of weeks I talked to her about how 'soon we'll stop having milk at bedtime' and how 'big girls have a drink of water before they go to bed instead of milk' Just light comments, not making heavy work of it. Then, I said 'in 3 days we'll stop having milk at bedtime' - 2 days - 1 day . I had to delay because in that time she got a chest infection and I thought it was unfair to do it while she was ill. So, when she got better, we did the 3 day count down again.
Then, on the first 'no milk' day, I said to her - we'll have a story on my lap as usual, then into the cot and I'll tell you another story in the cot. She protested a bit going into the cot - I offered her water instead of milk (which made her quite cross). Then I said - lie down and I'll tell you a story. Eventually she did, and I told her quite a long bedtime story (about a girl just like her who has adventures with cuddly toys just like hers...). Then I said 'I'll sit with you until you go to sleep'. We finally settled on her holding my hand. She fell asleep relatively quickly.
For the next few nights she asked for milk each night, but accepted not getting it - and fell asleep very quickly. A week later, she has stopped asking for milk.
However - big caveat. I think a BIG factor in this was the preparation - the fact that we'd talked about it a lot beforehand over a couple of weeks, and so she'd begun 'processing' it in her mind. I didn't just spring it on her. Also, I felt she was ready to do it now - not at a super-clingy phase, or unwell or having any other big changes in her life.
Now she falls asleep with me sitting in her room (very quickly). My next step will be to get her to go to sleep without me in the room. The way I did that with her brothers was to start saying 'I just need to fetch something' or 'I just need to pop to the loo' and leave the room for literally 10 seconds and come back. Gradually I extended the time I was gone, until the magical night when they fell asleep before I came back. After that, I was able to just say 'goodnight' and leave them to go to sleep.
You will get there, but you need to have a plan, be gentle, and talk to your DS about what's happening. And make him feel loved and supported through it - just by different means than the ones he's used to.
A good book is the Millpond Sleep Clinic one, if that's of interest.
Good luck. I know how exhaustion feels and how hard it is to think straight about what you're doing. But there really is an end in sight.