Originally Posted by PolyKat
As far as him dating someone and how that helps me, I need him to see first hand that he can feel something for another woman and still love me the same.
The thing is, this is not necessarily true. Not every mono person is a poly person waiting to happen. It may well be, if he feels staunchly mono and doesn't get poly, that he really is just wired that way, and that if he falls in love with another woman he might, in fact, fall out of love with you.
This is why I would never, ever try to nudge my mono partner into dating someone else. If he ever wants to I will support him every step of the way, no question, but as long as monogamy feels right for him I am going to accept that and not assume he can be anything else.
Are you willing to take the chance that your fiance might not work the same way as you and might leave if he falls for someone else?