I mentioned this before... KNOW EXACTLY what your FT's affair busting strategy is so you are both working in teh same direction and are not at odds... you could end up undoing each other's hard work... you really need to TALK to this FT and know what they thinkand where they are going.. and HOW they are planning to get there...
What is their marriage saving plan? how do you fit into that? This stuff is what you need to know before you approach yoru husband with ultimatims like this... I woudl even want to know that before my H went in to meet her...
Dont' work in a tunnel... it is at high risk of being counterproductive ...