@CoastalRat,
I have no issue with you snooping on FB in instances w
here they show strong signs of deceit / untrustworthiness (otherwise there should not be any reason to do so). But I seem to be in the minority here with such views in relation to privacy.
Nor do I have any issue with you getting upset with his behaviour, though I wonder how good friends they are, which is something you haven't covered (some people remain very good friends afterwards, which could explain his & her behaviour).
In terms of how you handled it- you could have handled it better (we can all improve in one area or another). In this one, you talk to the person. You stand up for your emotional needs. You consider his perspective. You try to work it out.
If it doesn't work out no matter how much you try, you move one.
But you don't destroy his belongings.