1. I'm very confused about this block and are confused on what it's really trying to convey. She says "breeding activities" but she's actually talking about her life and going through school and training, FYI, but the two variations below sounds very awkward so I'm unsure if it's right.
I think she's talking about high school kids getting down and dirty, in a cold and clinical way. Also, I think both club activities and breeding apply to 真似事
E: "Since I didn't have to deal with silly little things like clubs or reproductive activities, I was able to focus on was studies."
This means to "act your age," or to do something commensurate with your age. Something like telling a grown adult to stop arguing over who took the last candy. Usually the implication is that's NOT what's happening when the speaker says it. Google also seems to show some hits for people people paid wages which are lower than other people their age, but I feel those are outliers. Still, same meaning.
Gonna need to know the word prior to 勢い, or context if there isn't any. It would mean something like "driven by" or "caught up in" ... and then whatever word was prior to it. Basically, it's the feeling of inertia and speed of a car picking up and not being able to stop.
"I got caught up in the moment and just wanted to punch a few people."
"Heh, well, don't worry about it."
Hmm.. tough one here. Not sure on context. The random reference to baby teeth is weird too. Umm.. roughly:
"Saying you don't know is like asking why you're a baby tooth."
... no idea.
"After you put your life on the line, you really gain an appreciation for it, don't you?"
"Well, I thought at least you'd understand me."