I don't see how you can work with it either way? If he's lying, you don't like that, even if he ever does come clean and say he was doing it to keep others away, etc. because you don't know what else he'll lie about and he's been doing it too long now. If he's telling the truth, I don't like that she isn't seemingly in the picture (I don't respect her, if she exists, for "allowing" that) AND that he's flirting heavy core.

Does anyone know her name? Maybe she is posting on his page occasionally. I'm married and we're both on Facebook but neither of us "full-time" and when I was, my husband still was not but I think both our pages say the other is our husband/wife? I would ask him her name and look for her on his page, etc. and ask what the story is if she's not around. Call his bluff and/or drop him before you get more involved and find out more lies or are lied to more, either one.