You can create "distance" by not replying to his e-mail messages quickly upon receipt (don't know if you are)... anything like chat or Skype wouldn't help change the dynamics because it's in "real time." If he calls you on the phone, screen your calls. Call back on another day. Same with E-mail. You're more in control.

I would only do communication that is not in "real time." You are setting a safe boundary for yourself that way. He's stomping on your boundaries so put that in place, IMO.

He seeks immediate gratification and he thinks he may be able to get that from you. Be friends via e-mail or screened calls. Just don't flirt back...he may liken it as a "pursuit" and that could encourage him. Talk as if his wife is listening in, think of it that way.

I think you can diffuse the situation significantly by doing the above. If he still carries on flirting:

When you talk to him....you can get the message across clearly and without drama. For example, say his wife goes out of town again and he suggests you visit him. Being his friend, you could say, "You sound lonely, are you doing ok? By the way, tell me how your wife is these days. I'd love to meet her in person, so if I was financially able to afford to visit...I'd like to come when you are both home."

He will get the message right there. You won't have to "call him out" or embarrass him. I think it might be worth continuing the friendship as people make mistakes and past times he has been a good friend. Keep the boundaries up, though. It's healthy for you, especially since you have men flirting with you online a lot. (You might want to instill boundaries in that regard, as you said you feel vulnerable.)

If he still presses you - I would end the friendship...directly or fade him out. Whatever works for you. He'd really be trying to use you if he kept the one-way flirting and encouraging the "wife's away" invitations.

I hope that helps. Don't stress too much. I've read one of your posts and you're going through hard times. This isn't something you've done wrong and you handle it however you like. And that could be to do nothing for now...or ever. He will move on or he will work on his own issues with his marriage and stop his current behavior.

I agree he's being inappropriate - his wife would likely be unhappy if she knew what he is doing (flirting, asking you to visit him while his wife is gone). Being that you like him (as a friend) and liked communicating with his wife,