Legion assassins are after you because you have a bad reputation with the legion. Just don’t do anything they will hate you for, and you’re fine. You can also wear their armor as a disguise.
I never would have tried that on my own, as there’s nothing in the game to give me a clue that they’re connected
It has to do with a plot point that you wouldn’t know about yet, its not supposed to just be a break from the legion assassins.
Probably not, but you can kill the leader later once you’re better equipped to take on assassins. He’s one of my least favorite characters so I always kill him unless I’m specifically trying to help the legion.