Erin, I'm so sorry that this is happening. On the one hand, you left to take care of yourself. And now? It's all right back in your lap! Like some reoccurring nightmare!
I can relate... In my early twenties I was married to a man who was a recovering crack addict and alcoholic, and later he developed a sort of schizophrenia and so began his pill popping career. I had left him, as he was one scary person to be around.... My lawyer could never find him to get the divorce finalized, so I stayed "legally" married to him.
Two years later, the DAY my restraining order lifted against him, he showed up at my job. I looked at him and said, "No!" and I went and hid, and he was escorted out of the building. And two weeks later, he was found dead in his van in a neighboring city. The results for the autopsy were also inconclusive but they "found an empty bottle of pills" next to him.
I felt an odd sadness, I felt guilt, I felt relief, and all sorts of other weird emotions I couldn't put my finger on.
I wasn't left with any of his debt, but the call came to take my official statement, and I found out that he had a different name than I knew him by, and was also 5 years older than I thought he was. Yeah.... NEVER really knew him at all.
And so the next set of emotions became, "what is wrong with me???"
I'm still working on that answer, or rather, I am now working on a better question.
My heart goes out to you. My only suggestion would be to get support for the days you have to spend physically being there around his things, and take this as slowly as possible, and don't get who you are or how you feel entangled up in the mess he left. It's his mess. It was his life. It was his journey. And, if at all possible, detach from any responsibility you possibly can. My late husband's parents stepped in to take care of most of the necessary procedures.