Originally Posted by
Mashabo 
I do it because I still try to wrap around my head the fact that he might be sober, but doing all this.
So for something like that, you might try looking at both sides of it. I don't know if he's sober or not.
So, let's say he is sober. Has he become a great guy! Full of fun and laughter, kindness and loveable qualities? No.
Now say he isn't sober, does he fit the description above? No.
So really part you are struggling with is, where did the nice guy you knew go? What was he like before. I know he said he loved you and you are the one for him and all nice romantic things, but what was he actually like?
Well, you moved to his country, after 4 months he proposed, he was sober (apparently) for at least a year, after that he was using.
So what was it like between November 2017 and when he went to rehab? From your first post it was horrible. He was texting some woman telling her he was divorcing, he tried to patch things up with you when you said you were leaving for another country. Then while you were away, things improved for a few months then fell apart again. You returned and he wasn't even very good at keeping in contact.
What I'm saying really is, he actually never was a "nice" guy. He has treated you horribly, over and over. He is a cheater and a liar, he probably always was.
Perhaps he wanted to try the straight and narrow with someone. Find a nice girl, get married, make plans, but then it all fizzles when he goes back to his drug of choice.