I cant get the time line of Rory Williams straight in this episode, first it appears he is sent back by an Angel, hence why you see his grave in present day NY, before the Doctor is able to get to NY.
So that explains the old Rory in the bed, who is seemingly mistaken for Rory who was about to be sent back in time, by the Liberty Angel, and never actually goes because he kills himself. Creating a paradox.
So the paradox plays out, and we are back in the present, where Rory is again zapped back into the past, can the Angels feed on his life energy twice? Rory would not have had any energy to feed off, or was the first time paradoxed out of time, despite us seeing the grave at the start of the episode.
the problem with this half of the series, is that its trading water, we all knew Rory and Amy were leaving, and they had already had a good exit, so really it felt like the show was hanging around until the new companion joins, which is something that Doctor Who should ever do.
River kinda sucks the fun out of the Doctor in this episode, or was that Rory and Amy deciding what they should do.
In the end Rory is zapped back near the end of an episode, after everything seems like its ok, not unlike when he was wiped from the universe by the crack, only this time Amy goes with him.