How to deal if the person i love, desperately nned help

I will try to synthetize as much as I can this even though to story itself is hard to be explained and I don't have the best skills in trying to be short.
 I am in a relationship and I truly love a  person that really deep emotional issues and wounds. I know we all have them at certain level  but there is a lot and while he is hurting just himself if alone, in a relationship the other person is also affected. 
He doesn't know how to receive love and affection, he often says that he feels that he does not deserve love. He says about himself that he is mean, he is devil. I have asked why and he says because I hurt people but there is no clear example there given by him. 
Each time things are going normal and  we are good he needs to find a reason for "destroying" it. Is like he doesn't know how to live the good.  He starts changing mood from the smallest little thing. He connects it with other things and start a full drama from there. I know, I am trying to understand that the aspects he gets angry with is not the real reason and I don't take it personally, I am trying to understand it but I can't help it and is affecting more and more our relationship transforming it in something toxic in those moments.
He has anger issues. when somethings bothering him and changes mood is like he is blind can not see/listen anything else.   As I said  he starts from the smallest little thing. He is sorry after but I have tried to explain him that the solution  is not this, is to realize he can't continue in this vicious circle and he needs to see the real source of it. His thinking about himself is so toxic. He even gets to say I am mean, I have problems, I am so mean a cancer will eat me soon. When he is sorry he tortures himself with this thought.
He said this recently when I have tried to stop our relationshiop as much as it hurts me to do so buut I can't see what I can do anymore. He said " I  like to suffer...and make suffer...then Im sorry...I suffer so much...but then I come back to there... I like hurt... I love the sweatness coming from the hurt. I have deep problems...Im sick...Im dangerous.  I will never find a Love like you in my whole life...I know." He even took screenshots of me with tears when I had a breakdown finally (we were on video call that moments) because he said that he wants to remember it and use it to calm himself somehow .
I have tried so many times to explain him that the solution is not to blame endlessly but to realize that the issue is in this toxic thinking and try to see what really there. I was ashamed to tell him directly go to therapy but I said he needs professional help.
Lately I did something wrong I have transformed exactly in what I didn't wanted and in what I was taking care not to transform myself in. without realizing, I somehow became his therapist. not in the meaning that I a=have tried to analyze where x aspects comes from deeply but just to insist on the fact that the things are not as they seem and insisting there is something deep here.
he tells me I am so sweet and I give him so much good and he doesn't believe how I didn't run from someone like  him. He tells me when he is sorry that with my love and way of being I am helping him but I HAVE TRIED to explain him that I can be with him as his lover, hold hishand, give him the beauty love and sweetness that he talks about, enjoy our connection but I can't help him with finding the deep source of his behavior. And that is needed for his good. With me or without me he hurts himself, he has the same thoughts about him, about his life  and he says I am bringing only good in  his life but  we are getting to very toxic moments when I also can't get over things, and this is not the solution anyway.
I think he see me as his salvation, he always says " you took me in your arms from the beginning" Is not healthy at all to be his salvation, I can\t be and I don't want.... we got to very bottom things and I told him directly he needs professional help he needs to go to therapy urgently. I kind of gave him an ultimatum even if I didn't use this exact word but I said that we can continue our relationship if he asks for help.

I feel guilthy, I am lost I don't know what to do. I do not want to change a person but he is hurting himself even alone not only with me with the way he sees himself. I explained him is the bootom and that we can not continue this vicious circle of tense and than sorry and that this happens because of deeper reasons his behavior have deeper reasons. he said he doesn't want to loose me but this is to toxic, I really feel if we continue like this we will get very bad.

How can I handle better this situation?