I have just found out something that my LDR guy has been doing over the past few weeks as well and it to has changed everything.
It's not as severe as what you describe and he told me himself as he didn't even think it was a breach of trust so, again, different.
But I completely get how your feelings have changed. Mine have to. I still have love but I don't have any trust and I cannot see how to reconcile anything.
We all have our lines in the sand .. perhaps you have reached yours and that is the end of the line for the two of you.
Sorry it went down that way.
I am not coming from a poly perspective here so I am sure that others will have far better insight and advice.
Hang in there.