You poor things x my little ones used to get like this, totally wound up and wired and not able to sleep even though exhausted .. Looking back I was also so stressed out about it and frustrated ai probably made it worse (not saying you do this, pretty sure i had post natal anxiety.. ) A couple of things that worked for me and him were:
Really really loud white noise, on phone quite near his head while rocking him in a dark room after a feed
Feeding and then lying down on bed together rubbing/ firming patting him and shushing him loudly or again, using white noise
I know you say he doesn’t like sling but this was a game changer for us as he was often so overstimulated and wired that the carrier helped to keep him tightly close, pat and rock, bounce, sway , jiggle - add white noise and even though mine would fight it initially and cry, the look of utter contentment and surrender just before he fell asleep was quite funny. Mine initially didn’t enjoy carrier but a friend with a nap and sleep fighter encouraged me (forced me!) to keep trying as it was best thing for little ones that struggle.
Take a bath together, keep lights low and get everything ready for bed / sleep afterwards
Use a birthing ball to bounce him to sleep
Side to side rocking and, white noise! and ticking and stroking his nose , eye lids (sometimes he dropped off and other times he hated it..!
Get a cup of tea, find something to watch on tv, curl up with him and ignore him as much as possible in the hope he will just drop off.. (worked quite well if he was exhausted..)
Accept that some days he is going to have crap sleep, try (so so hard i know and i found it almost impossible..) to accept it and think tomorrow in another day and hopefully his night sleep will re set him.
Stay strong and hope you have a good night xxx