There is such pain in your words. I hope you can find a way to recover soon.
That said, your wife isn't poly and you have not been living a poly lifestyle. Your wife has been cheating on you. Simple as that. It is a horrible thing to do and your hurt is clear.
I don't understand why your wife is now destitute and your daughter is facing life without her mum? I know that you and your wife are having problems getting along but I don't understand why that means your daughter has to suffer?
Sounds like a horrible situation but blaming poly for it makes no more sense than blaming marriage.