Will he take a dummy? Can someone else settle him to sleep for the first stretch for a few nights/a week?
I have been working on breaking feed-to-sleep with my dd at 3 months old. She was super un-put-down-able and I can't bear crying, so it took about a month to get to where I am. Here is what I did: for the first week or so, I fed her to sleep as usual, cosleeping, then when she was finished I moved her a little on the bed just to rouse her slightly and see if she would resettle. If not, just fed her back to sleep and tried again a couple of times depending on how tired I was. It was usually easier as the night went on, when she was already nice and sleepy.
Then I worked up, v gradually, to placing her in the bedside cot after a night feed (sitting up in bed) and resetting her with shushing/patting/rocking her swaddled up. At 6 mo swaddling may not be an option, though.
Then, I worked on the first put down of the night. This I found harder as she would be more awake, and I'm still working on it now. Basically, I've set up a bedtime routine and some cues like music/white noise and keep to mood extra upbeat, smiley and positive so she doesn't fear bedtime. Then, feed til she dozes off, into the bedside cot (always wakes her), and i give her smiles and kisses, turn out the light and sing to her while patting/rocking her and sushing. She goes off sooner and sooner, though she has mastered hand sucking also which probably helps her settle.
We are in the grips of the 4 month sleep regression now, but at least she sleeps okish for the first stretch, and I tend to bring her into bed for the final stretch. Apparently, it's the later sleep cycles which are last to mature and consolidate do I'm just waiting it out for now.
The goal is to feed her and put her down to settle in her cot eventually.
I feel for you with the sleep deprivation, I really do. I still have bad nights when I wake due to her sleep noises and can't get back to sleep, and the improvements I've seen are recent so I still have a massive sleep debt. But it's different when you're hopeful and optimistic that things are moving in the right direction. Makes all those weeks/months of 3 hours sleep a night a bit more bearable I think. Very best of luck.