Does it mean anything if a guy private messages you on facebook for your birthday instead of writing on your wall like everyone else?

He's 41 & I'm 26 - I met him a few years ago & we're not quite friends but we're more than acquaintances. I had feelings for him for a while but then i found out he has a live-in girlfriend of 7 years! We have a couple mutual friends, who I feel like are hinting to me that he likes me - one always asks me "have you seen (guy)?" or says hey "(guy) was just talking about you - he says you got the fellowship!" & the other once said "(guy) REALLY likes you" Every time I see him, we hug each other, the conversation flows really easily. He's asked me if I'm seeing anyone and what my approach to dating is, &also our mutual friends have told me he asked them about me. Idk I just get the vibe that he likes me too but then I doubt myself bc of the gf situation

I moved across the country for grad school 2 years ago, & since then, every year he fb messages me to say happy bday, asks me how I've been, tells me something about himself, & then we have a conversation for a few hours, even though he can clearly see that hundreds of other people wrote on my wall instead of private messaging me. For everyone else (that I know of) he writes on their walls for their bday - he only private messages me

I still have feelings for him, but I live across the country, & I also don't want to do anything while he has a girlfriend - basically i dont want to break them up, but i would date him if he were single

what do you think all this means? Does he like me, & if so, how come he hasnt made a move?