Is Halsing supposed to be a fix companion?

I am wondering to put him in my team but is he supposed to be a companion or just a temporary follower?

And when I say the word COMPANION, I mean, does he has approve and disapprovement system like the others? Also based in his approval, do i unlock unique cutscenes and also, can I be sure he will stay until the end of my campaign in case I dont myself kill him?

Im afraid to equip items on him and then after act2 or somewhere in the history he simply disappear with my items and i never see them again. Also if he doesnt have an approval system, I'm just wasting a slot in my team, where i could put another companion which i could improve over time my relationship with and unlock new cutscenes.