Ah, to be young again, when you could say ridiculous things and actually believe them.
Rube, I'm twice divorced, spent the time when not married f'ing anything that moved, and am now finally happily married after hitting 40... I know young people don't believe anything old people have to say... but I'll give you one word of advice - relax. Don't take yourself so seriously. You'll get older, your views on marriage and relationships will change, probably several times. Your girlfriend does not mean it when she says she doesn't want kids. She may not know it, but she is lying.
Her father is just acting like all fathers of daughters would - to him you are just some punk who is wasting his princessess' time. So, don't get offended, have dinner with him on Sunday, and relax - if you miss that Bengals/Browns game, the world will not end. I used to watch every sports event I could, but with every year that passes, I care less and less. Really, just relax - life is a lot more enjoyable, if you don't take everything as a great hardship or a personal affront. If you fight a duel every time you think somebody disrespects you... you'll eventually lose...