Like you, I had an ex-husband, a little less than 2 years, that was my own personal horror story.
I too am now married a bit over 20 years to my husband.
If I had remained with the first one, I'm not kidding when I say I may have killed myself. I seriously considered it while I was with him.
Oh....to the OP....you also asked "Why do you think he gets mad so easliy over really small things and threatnes to break up with me everytime we get into an agruement?"
Short answer.....Because he knows he can. You let him do that.
He knows the way the scene will play out....He gets angy over nothing, a fight starts, he threatens you that he will leave you.....then, you do your part by one way or another playing the role of the person who "gets him to change his mind"
It's a really crummy play that the both of you act in day after day.
Imagine what would happen, I mean really happen, if the following happened....
You get into your usual fight over nothing, he threatens to break up. This time though, you're just tired of it all. I mean really weary to the bone of this revolving door. It's just ridiculous because you know tomorrow, or the next day, it will be the same thing.
Really imagine this. Imagine how tomorrow, next week, next month, the same stupid tiresome thing is just going to play out again and again and again.
But this time, when he makes his idle threat, you just say, with no malice or thought of "this will show him" or "we'll be back together tomorrow." oranything like that, you just say "All right, we're broken up.", and you pick up your bag, and with no drama, just say "goodbye" and leave.
How does the thought of doing that make you feel? Maybe relief that you're free and can move on?
You can bet your bottom dollar that he will call you, text you, come by to either apologize and let you know he's going to change (he's not) or to continue the fight and make you the bad guy.
If you accept this, then where will you be? Back at square one. Except that now you have 2 years and 2 weeks, or 2 months more of this crap.
Or you can just keep things as they are, and experience 2 weeks, or 2 months more of this crap.
Or, if you were to decide to move on, you would be uncomfortable for 2 weeks or 2 months, then realize how much freer and really happier you are, without fights and threats all the time.
Just a thought.