bro, this is turning into an ordeal. I don't know if this has been brought up yet, I only read the first few pages and the last page, but let me just say something. I think you're turning this into some huge issue that it shouldn't be. I know exactly what you're going through, I've been in the same situation plenty of times. But when I finally just got over it and treated it like no big deal, it really was no big deal. You talk to your friends right? Do you stay up all night worrying about how to approach them or if there are certain rules about asking them to hang out and such? No, because that would be silly. They're your friends and they dont care how you go about things. Its the same with girls. It doesn't matter when you ask for a number, when you ask to hang out, or why. If shes interested in the slightest, she wont look the other way because you asked for her number after 3 dates/hang outs instead of 4 etc... It makes things a lot easier to just be straight foward enough and avoid making things overly complicated. If she asks why you need her number (which no girl will ever ask if they think you're cute/nice/whatever) just tell her exactly why. Ex. "I might need to call you for help", "so we could maybe get together sometime". Something along those lines you know? The point is, that its not a big deal unless you make it one. Girls are people too, no reason to treat them like some unobtainable thing. Being friendly will get you far.
Also one other point, I see you already found a different girl to consider. Thats a good thing. This might take some time to get used to, but you said you noticed her looking at you sometimes. Thats a good observation, and its also good to know that while chasing girls is fun and is definitely worth the effort sometimes, theres also a flip side to that. I've found that if its a large enough setting like a mall or your campus for example, there will almost always AT LEAST be one person who notices you. Then make your move. Its good practice to be on the other side of things sometimes. Learn how to flirt, talk, maybe wait until they ask you to do something. You be the person that they want to hang out with and talk to. It really helps to kind of see what its like from the perspective of the girl you find attractive. Good Luck man, practice makes perfect.