Explanation On Gaining Battlepoints?

Can someone or developers, Please provide an explanation on how the battlepoint system works.

Because one minute I could be making crazy points as an officer dishing out one buff and standing at the objective doing almost nothing but freak out that I might get shot in the face and die. Next minute playing as an assault and getting a 7 person kill streak then get shot in the face, die, repeat and it gets me very little battlepoints... I could play as a AT-ST get some kills, die, make little points, or play as the "sub hero class" (death trooper for example) get some kills and so on, die, and make very few battlepoints. It makes me ONLY want to play officer.

The only one I understand is that playing as a Hero makes little battlepoints so that said person cant play as Kylo Ren get 15k points in one go, die, then come back as Ren again. That I totally understand. The others though not so much.

I understand that teamplay is very big to gain points, but thats very broad. I've heard that playing in a squad is big for gaining points but what about with friends, friends that you can actually work with as a team. If they arent in your squad how does it work then?? Do you still get points by working with them outside your squad???