1. He tells Carrie that he always been this way. He of course was not talking about the deficits from the stroke. He was talking about the rage inside him, ever ready to boil over against enemies, or even in pursuit of his work. And even when rage isn't part of it, he's been all too quick to injure and kill when necessary. He shot Carrie, and killed a boy in South America, all on behalf of missions. Peter's self-awareness of this dark part of his psyche is an important piece of what's going on, and what' going to happen.
2. Why is someone posting dangerous missives online under Quinn's name? My guess is the poster is likely Dar or his agent, and the goal is to set Peter up as someone who needs to be terminated, which Dar now will only be too happy to do,
Which brings us to the teaser for next week's episode - it will change "everything". Peter's death would certainly do that. It would, in effect, free Carrie in all kinds of ways. Much as I would hate to see that happen, I'm guessing that's what we'll see next week.
But there's an outside chance it will be someone else who's shot or otherwise blown off the the show. Wouldn't it be nice if that was Dar? That would also bring in a breath of fresh air, and certainly just about everything Dar has been doing this season makes him an appropriate candidate for justice in the extreme.
But justice has never been what Homeland is necessarily about, so we'll just have to stay tuned and see what happens in next week's finale to this provocatively pertinent season, including crowds shouting the familiar "not my President" to the President-elect last night.
And see also Homeland on Showtime ... Homeland 1.8: Surprises ... Homeland Concludes First Season: Exceptional