Is it right to rehome my cat if he is stressed?

A year ago I moved country with my 6y.o male cat, I've had him since a year old after my grandad couldn't look after him anymore. He was mostly used to just me being around and I had to move out of an abusive household that was hurting me and my cat.

At first with moving in he seemed pretty happy but confused he's in a bigger house now and getting used to a new person and biggest of all he was meeting a dog for the first time (my partner had a 12 year old medium dog who honestly thinks hes a cat so we knew he would cause harm to him since he was raised with cats) and we introduced them slowly and my cat didnt like him much but he tolerated him and just kept to himself.

He didnt care too much for my partner he would let him pet him and liked being fed by him but he wasnt the most cuddly.

He relaxed more over the months and started trying to play with the dog a lot so we thought maybe he was getting lonely and would like a friend so we made the choice to adopt a brother and sister kittens, we introduced them slowly and my cat enjoyed playing with them but not much else he didnt like them coming up to him or sleeping near him.

Problem is now over two months my cat has seemingly gotten so much more stressed, he hisses at everyone even me and sleeps most of the time, for the first time he's been chasing the kittens and actually trying to hurt them, and today he was sitting in the hallway with the dog and then hissed and swiped his eye cutting it. We cant really walk past him now without him swiping at our legs and feet and hissing.

We have 4 litter boxes and everything is kept really clean, he doesn't spray at all. I've followed all of Jackson galaxies advice even trying reintroducing pets but it seems my cat just ends up getting too upset and hes honestly never seemed fully happy in this house. He hasn't got any health issues hes been checked by a vet.

I feel I cant properly care for him anymore, he won't even let me pick him up anymore or he will hiss and scream when he used to beg me to pick him up for hugs. He doesnt really want us near him unless we are alone in a room with him which isn't very easy in this house. We have made adjustments for him and we make sure to only touch him if he is asking for it and we mostly keep him in a separate room from everyone else since the rest of the pets desperately want to be around us. I just want my boy to be happy and I'm realising maybe he would only be happy in a household of no pets and maybe only one person since thats when he always seemed happiest.

My only other idea was to see if he would like to go outside in the garden, we got an airtag collar which is breakable if snagged so he cant get stuck but maybe he would prefer being outside and away from everyone but I worry thats not a sustainable life for him.

I feel he'd be happier somewhere else but it genuinely breaks me having to give him up but I feel he would he happier with someone that could give him what he needs.