1.)
I think that this shows credibility seeing as to how he has so much experience. It is one thing to cite a source & then go study it, but in my opinion experience is way better than getting your knowledge from somewhere else.

2.)
He knows that Fb (football) & war are two things that his audience knows a little bit about so he uses those two things to compare knowing that he can find similarities in the two. In paragraph six he shows that the lingo of Fb and war are a lot alike.

3.)
He makes a quick & smooth shift by bringing in another aspect of the game. That its all fun & games when they are practicing or before a big game but when the pads go on & the ref takes the field its a whole different situation. He goes from a playful almost fun tone to a more serious tone.

4.)
It adds to his credibility & it shows that Fb is a lot like big business, you do what you have to do to get the job done even if it means having to endure a tiny bit of pain.

5.)
He counters this claim in the 16th paragraph. “What organized football did for me was make me suppress my natural urges and re-express them in an alienating vicious form.”

6.)
Soccer and b-ball have the same kinds of lingo. I’d have to say almost any contact sport, shoot even some non-contact such as baseball.

7.)
No I don’t think its necessary for the audience to know about Fb. It does help but it really doesn’t make that big of a  difference for the examples he uses. It seems to me that his audience is men or people who have played Fb because they can relate to what he is writing.