May I wade in?
I think Sherlock and Moriarty's little "tea party" is much more significant than anyone is giving it credit for. If you think back to the dialogue, Moriarty plainly tells Sherlock how he's going to "burn the heart of you", tells him he's told him, and tells him what will happen: the fall.
He even says something along the lines of falling being like flying, but with a more permanent destination. All the visual and verbal clues re: angels and Sherlock being "on the side of the angels" - well, they fly, don't they?
OK, it's not an explanation (yet!), I'm still working on it.
But it is Sherlock who falls, the disguise/mask that may have been used in the kidnap is just a red-herring insofar as the fall goes. It plays a part in planting doubt into the police team and Lestrade, end of.
Sherlock fall is broken by something enough to cause him injury but not kill him. The pulse is neither here not there either - a full fall from that height will either smash your head in or cause significant internal damage, he's toast, pulse or no pulse. Why taken away in a stretcher so quickly? Well, they are outside St Barts, wheeling him in for medical attention seems sensible, he's not being taken away covered over, is he?
The fall as witnessed by Watson, despite the accident with the bike, is fluid. My guess is he fell onto truck and flung himself onto floor from there straight away - he can cope with hurting himself, plus has blood pack (hands behind back earlier?) to egg it on. Molly is needed to certify death, swap bodies, nurse to health, provide hidey-hole.
Boy, better stop now and go back to work!