Hi theexwife, first of all everyone is going to grieve in their own way, there is no "normal" in grieving so if your ex mother-in-law or his ex wife blame you for the way you're reacting either they don't understand or they're in pain themselves/not able to see past their own reactions.
The way I'm reading it though you don't feel it's OK what he did, you don't think it was maybe right but you understand why he did it, right?
I mean he shouldn't have had to suffer the way he did, or do what he did, if there were any other answers available to help take away that pain he felt/the way he felt.
But often in that situation people just can't see any alternative and the depression just puts a wall up between them and seeing things any other way. And sometimes whatever people try to do to help, just isn't going to be enough.
And now you, it sounds like a really difficult thing to cope with considering the connection you had with him, maybe it hasn't hit you "full on" yet?? But sometimes something like that can catch up with you at any time, so I hope you're getting any help you need with the way you're feeling, or get help when/if you need it.
And remember we're right here for you too.
Alison