Hi, 1Blueglass.
Welcome to SR.
Very sorry for your loss.
It sounds as if your significant other had a lot of issues and problems..
I appreciate that you want answers, particularly regarding your role here, but you may not get them.
Not now, not ever.
Do you have someone you can talk to about this?
Someone who is not related or friends with your former SO.
Time and distance will bring clarity, I hope.
Meantime, try not to blame yourself. Things may have turned out the same whether you were still together or not.
Take good care.