It has been established several times over the course of the series that Danny is the oldest of the four siblings, followed in order by Erin, the deceased Joe and then Jamie. But in the last scene at the community gathering, Frank speaks of "my oldest, Joe".
On his way out of the movie theater, Jamie tells Eddie that he had never delivered a baby before, but in a conversation with Frank in the previous season, when talking about the best parts of his job, Jamie says, "Hell, I even get to deliver a baby once in a while."
When Raymond is shot he falls flat on his back, left arm up near his head, right arm by his side. In the next camera angle he's on his right side, left arm over his head and right arm in front of him, still holding the gun.
After Ray is shot in the forehead and killed, his stomach inflates from taking a breath instead of deflating.
By using a pretense to illegally enter Raymond's apartment, Danny and Baez would invalidate any evidence they found.