Search Results: when other girls flirt with your boyfriend

I like this guy from college, we have hit it off well, we are good friends and we have known eah other for 5 months.
He is an introvert, very nerdy, gamer geeky type, while I find him attractive (like a 8-10), people look at him and are like "no" (2-3)
He only close to about 3 girls, one is me, one os a friend, and the other is a crush that brother-zoned him and is dating her own boyfriend right now.
People think I can do better (8-10 by most)
Some facts:
-He knows I like him.
-We still flirt (He only flirts with me).
-He constantly glances and looks at me for a reaction to things like his jokes, but especially if he is playing a sport.
-I am the first girl to like him, ever.
-He is very serious in what he looks for in a relationship (like best friends type of thing, he won't just date you after one inital conversation or based on your looks)
-He is afraid of loosing me as a friend if we date (this is from context clues from a talk we had, he told me about how friends turned s/o turned to never speaking again)
-He dosen't want me to change.
-We have long talks, like 5-10 hour talks, all nighters.
-He gets jealous/ curious whenever I bring up a guy, and will have a sigh/look of relief when I say were not dating.
-When I told him this summer about how I stayed friends with all my crushes (i. e not letting my feelings over whelm a good friendship) he seems a lot more curious/ interested in me.
-He dosen't talk nearly as much to his crush anymore, and while we don't talk to much because of ur schedules, he will help me whenever I call.
-He is not the type to take initiative if he knows that the negative outcomes outweight the positives.

So summer is almost over and he is about to come back down for college, we have what I like to think are dates, set up (we choose some movie nights, just the two of us, disneyland, etc.)

When I told him I liked him, he said he wanted to stay just friends, but these things tell me he changed his mind, did he?
And if he did, should I say yes?

This guy with a girlfriend was flirting heavily with me last night here is how the convo went
him: when you saw me you smiled and blushed you so wanted to jump on me and eat my face
me: I'm naturally shy and I smile with everyone
him: so you know I'm half Brazilian half Italian right, you know what that means
me: no
him: I have a third leg it's kind of a blessing and a curse
me: most men claim fhat
him: genetics speak for itself I can prove it name a time and a place
i ignores it
him: so would you like proof
me: I'm not going to do that to my boyfriend
him: our secret
me: I've been cheated on in the past I know what if does to someone.
Him: let's be honest your so young to be tied down (I'm 21 and he's 23)
me: my friends have been with their partners for three years plus they don't regret it and when I was single I never hooked up with guys
him: that's because you never met me

i ignored him after this. However I feel bad for the girlfriend in the mix not knowing her boyfriend is sleazing into other girls should I tell her, and is this an ego trip for him?