Agree -- if he balks at transparency, that will tell you all you need to know. You should then say to them "Then I can only assume you are in still in contact with her, or want to be able to. That doesn't work for me. Sounds like we both have some big decisions to make."
And end the convo.
The recidivism rate of infidelity even WITH good MCing, no-contact and transparency is fairly high. (25-50?) Without it? I'd put it more like 90%. Statistics aside, if this is something YOU need for your own anxiety and peace of mind, I wouldn't recommend you back off on it.
