Alright, first off. I am down with every reason you ennumerated. Girls are in fact, the anti christ.
Moving on.
Looks to me like you're going after the wrong type of girl. It really sounds to me like you're meeting girls in one environment then trying to pull the old switch on them afterwards and they're dazed and confused wondering what the fuck just happened, where did the hot bod they were ready to ride go and why is this timid geek trying to engage them in conversation. It seems to me that a girl confident enough to approach you at a party and compliment you on your looks isn't likely to be worried about being taken advantage of. In short, get thee some self confidence and move in for the kill.
e.g. here's what you should have said in that above conversation in order to remain in character:
HEY U WANT 2 POUND DOWN SUM BEERS LTR 2NITE??!?!
or
WANT 2 GO CLUBBIN LTR?
or the always trusty sleaze factor:
U BUSY LTR? I"M HOT 2NITE
Granted if you are interested in meeting girls which you'd be a better match for, it's probably not going to be at a party.
Disclaimer: I am a 20 year old practical virgin at a heavy party school (UTexas). I am in truth, the alluded morose hermit. I'm just going by what I see on a daily basis.
PS I seriously hope you die in a fire for insulting my WH40k figurine collection : ( SPACE MARINES! AAATTTACK!!!