Hurtloam, you might be making an error by trying to incorporate men into a circle of friends that mostly hang out with other women only. I suggest you develop a circle of friends for the single-gender night out events, and another circle of friends who often do things involving both genders. There can be a little overlap between the two circles (like a Venn diagram, or the Mastercard logo) but in general, don't set up events for the one-gender circle that you want to invite men to, and don't be surprised if your one-gender circle isn't keen on attending the mixed-gender events.
I think the single-gender thing is a statement that "on this occasion, I don't have to look sexy/attractive, it's just the girls (or guys) and I can relax." As someone else said above, it's sometimes beneficial to dish your gender issues with your same sex friends. (e.g., Why do men do this? When she says ____, what does it mean?) Dating and also marriage are sometimes confusing and stressful. Also, if one is already in a relationship, one may want to avoid temptations to roam, or one may want to tell the partner it will only be a same-sex night.
Your younger male friend that you are interested in, if you do things with him alone it will definitely feel like a date, which could be awkward, and I know you have a history of things that go nowhere and then disappoint you. So enjoy his company in a mixed group. If it's attending a play or a concert, ask if he has any friends that may want to come along. Feel free to bring along a few of your own.
_________________
A finger in every pie.