(A) your H has already filed for divorce as per the info in your signature line. You are reaching the one month mark on the filing so I would think (?) legally you will be required to respond in some manner pretty soon.
(B) Do not tell him what WON'T work as he already knows that.
(C) Anybody in an affair puts their spouse/family in the secondary slot while the affair is going on. Telling the cheater what is "obvious" is a waste of time.
If he brings up the D tell him your attny will handle it. If he brings up the M keep your boundaries. A M cannot exist with THREE people so talking about it while an affair is ongoing is moot.
