I don’t think Sherlock was able to predict what was going to happen on the roof. I believe he spoke to Molly beforehand because he thought he could jump as a last resort. He must have known the exact height of the building and some certain ways to fall which, if mimicked correctly, would allow him to possibly survive. As many of us noticed, he fell in a very strange manner, almost as if he was flailing. He most likely used one of the hinted-at methods for stopping his pulse which have been very popular theories on Tumblr (i.e. the rhododendron ponticum or the rubber ball trick). Molly would have prepared everything for his fall, and been ready to nurse him back to health to the best of her ability and help him escape if he lived through it. He knew that if worse came to worse on the rooftop and he was about to be killed, he could have thrown himself off of the building and tried to fall correctly while having his pulse stopped. Moriarty killing himself was a huge surprise to him and he truly was at a loss at that point. I’m assuming everyone who brought him in was in on it, homeless network or not. I think everything on the roof— the panic, the tears, and the willingness to die for his loved ones was all real. He probably knew that he had about a 50/50 chance of survival, if not much less, and that he was really saying goodbye to John either way. I think so many of the other little things, like the biker, for instance, were honest-to-God accidents thrown in there by Moffat and Gatiss (but mostly Moffat) to have us do exactly what we’re doing and theorize WAY off track so there is more of a surprise when season three comes around. I think 90% of it is still a huge mystery (what is throwing me the most is what happened to the body of Moriarty and why it isn’t in the news, and whatever the hell happened when they were locked in the cell together),  but this is my general idea of what happened. 

Why did he act so frazzled when Moriarty said he picked the perfect place to do it? And he was all “Do it? Do… do what?” He obviously knew and it is not like him to be frazzled.

Why wouldn’t Sherlock check his phone in the beginning when he always answers texts immediately? 

When he found the camera in 221B, why did he look so sad about it when John wasn’t looking? Also, why did his own image come up on his computer when he was holding it?

What is the point of IOU and is it connected to John saying “I owe you so much?”

Why is nothing ever said about the body of Moriarty being found?

And, somebody already addressed the fact that Sherlock was hyperventilating on the roof and that could have been significant and even helped save him. It’s quite unlike him.

I loved this monologue and thought it was just as sweet and gut-wrenching as the next guy… but when he said “I owe you so much,” I was like “that was a strange way of putting it.” I just NOW realized… the “I.O.U.” never seemed to have a point. Now, here is John, saying “I owe you.” Could this mean anything?