My bf choked and threatened to kill me during heated argument

I (19y) had a bad argument with my boyfriend (23) because I found out that he, as an ”ex-drug addict”, had relapsed already a month ago and has been using different substances daily since like suboxone and prepagalin not as prescription medicine but bought from street market. I was very mad about his using and lying and was insulting him over it on text.

When I got home I was talking about breaking up because he surely wasn't sounding like he had mind on actually stopping using. I was debating with him if the cats should come to me or him and reasoned with him that they should come with me because I have been taking better care of them than he had (taking to the vet, spending more time with them and usually being the one to feed them).

He said no. Because his mother had bought the first cat (girl) and given it to us, making it his. So he wanted to separate the cats and I was fully against it, knowing it would make them depressed, probably the girl cat he would be taking even more depressed and anxious because she easily gets easily stressed already with even a little change.

So I tried to reason with him by saying that he can't even take care of his own. Saying examples like him missing two teeth because of him having had neglected his teeth in the past while using drugs. Even on this date I have to remind him to brush his god damn teeth. Also he never eats if there is nothing cooked or even if there was he stills complaints of hunger and then does nothing to it.

I also said that the way he has been using drugs are clear signs how he neglects himself and everyone around him. How he neglects the cats and belittles me if I think something is wrong with them. Like last time when it turned out they had ear mites and he didn't even want me to take them to a vet in the first place because I was being dramatic.

Lastly I called him stupid to be this delusional and not see why I don't see him even fit to take the girl cat with him. I also said that he must be somehow aware of that or then he is even stupider than we all know. And that went to his feelings because he is insecure of his stupidness because he has been called that a lot growing up. He is a pathetic stupid loser!

Well when things got heated and he stood up from the bed and I continued making the arguments. He made me quiet by pushing me on the ground and choked me till I was struggling to breathe and the lack of oxygen got uncomfortable. While he choked me he said ”I could kill you right now and sit a couple of years in prison and move on.” (The prison sentences where I live are very short)

For a moment I thought he was serious because of how mad he was, but I shrugged it off at the moment. But now after an hour I think it’s very scary how he acted. He has never threatened or hit me during our 1.5 years together but this was something so out of character of him.

After that argument he calmed down and went to smoke a cigarette came back and said that we are not breaking up because he would be all alone and wouldn't know what to do without me.

The only thing still tying me to him is the cat situation because I want to save the both from his hands. I also know that after we break up for good he's gonna start using drugs way more and then he can’t properly take care of any pets and when he uses all his money on drugs then he has no money for sudden vet bills etc.

He said if I contact his mother (the one that bought the cat) to ask her who should take the cat, me the employed one with savings or his unemployed son that uses drugs after having relapsed, that he would destroy my phone that he had gotten to his hands and also lie to my parents that I use too. I never have even told my parents the true history of him having been a drug addict in his teenage years to early adulthood because he said not to and I was ashamed of that too.

So wtf I going to do to save both of my cats? Was his abusive act really as bad as I think it was?

Also sorry if my storytelling sucks.