1- the fact that he wants to be a hero just to impress Kara and be close to her is already a telling that he is not fit to be a hero. Heroes don't want to impress other people, they want to protect them..they put their lifes on the line to save completely strangers and nit just people they care about.
2- when did Kara…

Becausw they were hostages that could be used as leverage at some point. And he actually did that when he used them to make Lincoln surrend himself

Pike had the goal to wipe out every grounder, starting with that army, he only didn't do it because he knew he would lose…so sending of that "don't fuck with us messege" was the second best option. but if he had had the time and the resources, i have no doubt he would do it.

Jason on twitter actually said that it was not genocide…I mean…really?? how is that not genocide?

Thank you. I am glad I am not the only one who thinks that