Continuity mistake: When Amy lies down on the tree stump, her hair is all over her face, but on the wide shot her hair is behind her head. (00:12:46)
Revealing mistake: When the Doctor's jacket is being held by a Weeping Angel while he's monologuing about why they haven't killed him yet, he moves at one point and the Angel's hand moves with him, despite the fact that they're normally effectively stone in situations like this. (00:12:16)
Continuity mistake: After the Doctor finds out River's in Stormcage, when he pulls out of the pocket computer to look at the readings from the time crack, it rotates in his hand between shots. (00:19:24)
Continuity mistake: In the last scene, when Amy attempts to seduce the Doctor, she pulls his suspenders off his shoulders and he pulls them back on. As a result, the suspenders change position between shots.
Factual error: The all important date of 26/06/2010 and it ticks over on Amy's alarm clock right at the end of the episode. However it shows 11.59 AM and flicks over to midday (12.00PM) the next day. The date should've stayed on 25/6 or, as I suspect was the intention, the clock should've read 11.59 PM and then ticked over to 12.00 AM thus changing the date correctly. (00:41:00)
Chosen answer: 1) When Stephen Moffat took over he ignored a lot of what had been developed before (there is not in-universe answer). 2) It would have killed Rose, so the Doctor absorbed the energy. His body regenerated before the energy could do a significant amount of damage that would prevent regeneration.