do what you want... i can only advise based upon experinces.
beat him, good answer but in 5 or 10 yrs you may regret it.
arrest him, another good answer but a m ajor hassle for months to come.
restrain, not a bad alternative, butcauses resentment and also involves courts.
talk with the mgr. best, IMO short sweet and to the point, and can NOT get you into trouble.
I can tell you that personally.....
Been there DONE that. in all the scenarios listed. And on both sides of the table for almost each and averyone. and now at 36 yrs old(over a decade has passed) I wish that everyo0ne had been handled differently except for the ones that involved the little pow wow. Not to mention the money i spent to correct my mistakes that I made while trying out the other alternatives.
And do not invite him for dinner. ESP if he is a stalker or dangerous. AS well, because you just turned a simple matter, or one with a good ole buttwhopin (and fine) into a major hasle for you and your girlfriend. I cna guarentee you that the legal matters taht you would bring her into would cause her to hate you as well as the money it will cost you BOTH(she will likewise be arrested). PLUS, he will know where she lives, as wel as anyone else he wishes to tell. Not to mentin that some people may say they hate someone but if they get put into the middle of a fight over jealousy, they may swing sides too.
IF you have never been arrested, have the chat with the mgr. You dont want this to be ther first time, not for this. If you have, then make your own decision. But, dont come back whining about the outcome.