I'm glad you joined us and am sorry for your troubles.
If you read your post, it seems like you are looking for answers to understand him so you can save him. Sadly, there are no good answers when active addiction exists, and all the love in the world cannot save him, if it could not one of us would be here.
It's not you, I can honestly say that most of us have been where you are, with me it was with my addicted son. "What if he did this?"..."What if I did that?"..."He said he couldn't do it without me...."Why did he steal from me/lie to me/rage and turn my home into a war zone/overdose/keep drugs in my home/pretend I was selling an office full of computers and collecting money from victims who thought they had found a good deal?".
Trying to figure him out is futile. If he is willing to go to a rehab and/or talk to a counselor, they maybe can help him, but the key word is "willing". Until he is ready nothing will change for you and it will get worse with him.
Take a read around, that might help you understand more about yourself and what your life will be like if you stay with him.
We don't judge you here, or rush you either, and please know we are walking with you until you can find your balance again. You are among friends here who understand because we have been where you are and found our way back to sanity.
Hugs