Another thing you may not be considering is if you two get together, and then break-up (the probability of that is higher, due to the SA/SP), you will still have to see each other at the job, which may be quite awkward and painful. Thats why many advise against workplace relationships (especially if you are in a job that you really don't want to lose), and why some companies have expicit policies against it.
With that said, I don't think this guy is playing you (specially if he has SA, unless hes BSing you), like taws said, I think he is making up the "girl friend" because he may have the same concerns about dating someone while he's never had a girl-friend either (Ive lied about that before so I didn't look like a deperado). Plus, he's doing the "Seriously/Joking" bit because he may be afraid of rejection (remember, us SPers don't take rejection too well). If you grill him about the "girl friend" he may think not that you are trying to find out if he is a "Player" but that you think he is making the girl up. I know it sucks to get hurt, but I think everyone is just too damn defensive, these %$#@ing "Playas" over time has put everyone so much on the defensive, it's impossible for anyone but them to actually get a date (because they are the masters at breaking past these defenses, while us shy guys who want a relationship beyond the bedroom can't even make a dent)
TAWS- Can always count on you to add a little levity to a post :lol: you have a crazy but good sense of humor