As has been said so many times to me, LMN, YOU have to concentrate on YOURSELF.
I was married to my XH for 12 years and although he was not an addict, he was very happy to enable me to be a codependent, because it benefitted him and he LOVED all the attention and having someone wait on him hand and foot and doing whatever he wanted. But like Impurrfect, I knew when I had reached my limit and enough was enough. There was no going back after that and I also suffered tremendous guilt for a long time over ending my marriage - I still do. I've even gone so far as to believe that the reason I was treated so badly by the last guy I dated (an addict) and now yet again by this XA, is because it's punishment for ending my marriage and hurting my XH because he didn't want a divorce. Of course in my head, I know that's not true, but it doesn't stop me from adding that weight to the already-heavy burden I carry around with me on a daily basis. But through SR and hopefully therapy, I can change that.
It is NOT cold or selfish of you to be thinking about YOURSELF and what YOU want or don't want. You have gone above and beyond to be supportive and understanding, much more than many people would do in your situation, and now you must turn that support and understanding back around to YOU and decide what YOU want/need to do. And whatever that may be, we are all here to support you every step of the way!! Sending HUGS!!