Do I understand you correctly - you are only "allowed" to have one-night stands???
If that is the case, what a waste of time and energy for the women who start dating you and want an actual relationship. I say tell her now, before she goes out with you, the poor thing, so she doesn't get her hopes up.
Edit: Okay, I just read more, and the "it has to be a threesome with my wife" after the first fuck is really gross. It's like making a demand on a woman about who to have sex with. That is so offensive, I don't even know where to begin to explain why.
If I were you, stop dating right now, go to swing clubs and fuck your brains out, but don't go and use women seeking actual, real relationships with men who will be there for them without requiring them to be a sex toy for their wife. Ewww. I think your wife needs to work on her self-esteem and jealousy issues, as well as develop some respect for other women, if that is how she asked you to treat them. It sounds like neither of you are really ready for polyamory, truthfully, until you strengthen the foundation of your relationship so that you both trust each other and feel that nothing could threaten your bond.