oh, regarding the friends who "knew" you might change your mind. It would not have mattered if they told you 3 months ago. You probably were not ready to hear it then, never mind act on it.
And, regarding the OW, please understand that statistically, most relationships that begin as an OP do not last. It could take a while for him to decide to re-engage with you and also to end the R with OW. AND... he will need time to grieve that loss... so patience would be key, here...
