Why does he randomly continue to give me quest? I don't talk to him at all, and have even gotten quests from him when I'm not in Sanctuary. Is there a way to turn him off? Especially since he's giving never ending quests.

His missions do end after a while, but there are a lot of them. From what I've gathered, he sends you to almost all of the possible settlements, and only stops once that's done.

If that's the case for him, and the endless Brotherhood quests, I'm going to mash them all out. Horrible design to not be able to reject quests.

Are you tuned in to radio Freedom? If so, that will give you the Preston quests as well. I keep it turned off