Well you said the blonde was from school so was she your first love? Because that's significant and people rarely forget their first loves, even if there was no sex.
Maybe that's why you dream of her and not a current lady.
As for your XW, you mentioned recently (I think?) that she had taken meds again, so if she's still using drugs you likely can't get accurate or truthful statements out of her.
In my humble opinion, a lot of addicts don't do anything until they are forced to, and if that was me and my X had given an assurance he wasn't communicating with OW and then I found he was, I wouldn't let it go, I would not pretend I didn't know, even if that isn't DB'ing.
My X is still 'friends' with one of his OW, but he is upfront about it, not that I think it's acceptable, but it's better than lying about it. Sorry if that's a bit blunt but I wouldn't put up with it.
In fact, my X still had a book from EX-OW2 at his house, dated June 05 and with a sleezy message in it from her. He was out at the time, so I ripped the message out, tore it into pieces and threw it in the trash - I would have set it on fire but I was worried I'd make his smoke alarms go off
Then I put the book in my overnight bag and when I went to the hospital the next morning, I threw it in the rubbish bin Don't care if he notices it's gone, either.
