Re: "Do girls care about"
dont worry about a thing, im 6in at 14 but i dont think ill get any bigger (6in is average for an adult). maybe its like height you could get a growth spurt (in your penis, no pun intended) and grow a coupla inches (and thicken) at any time, and even get bigger than normal (like 7 or even 8 in!) but if you dont get any bigger, anywhere from 3.5 to almost 7 inches is considered normal.
On the cumming issue, most girls I know (I am not sexually active but we can talk about anything!) love to see guys come (ejaculate, that is) but they dont really care how much you come (as long as they see SOMETHING, they are really satisfied) but as long as you tell them how good they made you feel, they will feel really happy and wont really care if you ejaculated or not.
Hope this helps!