Let's put it this way. If Yuzuru falls 2-3 times but fully rotates his jumps, he will still win UNLESS someone like Javier Fernandez delivers a clean 3 quad program with no doubling. The World's are in Japan, and the title is Yuzuru's to lose.
That would just create a whole sh!t storm of hate for him. But if Hanyu manages to skate his SP cleanly, I think you are probably right about him having a 2 fall advantage. The highest Fernandez has scored this season was a 91 with a fairly well skated SP at Euros. However, if Hanyu makes mistakes in his SP like at the last two worlds, I don't see him having that 2 fall advantage over Fernandez. Hanyu's hit the 90s in PCS, but his PCS also have a big range while Fernandez's PCS consistently stay in the 80s even for bad skates. So I doubt that if Hanyu gives points away on the technical side in both the SP and FS, the PCS gap btwn him and Fernandez will be large enough to hold off even a decent Fernandez.
I'd vote Abbott as dark horse. He should just skate without the quad in the SP and put one in the FS. He'd probably get around the same SP score as Brown and that would keep him in the hunt. Who knows, maybe a couple of the guys going for quads will miss theirs and that would put him in an even better position. I think the best thing for Abbott to do is go for the layout that he will most likely end up skating clean and then play the waiting game to see how many guys actually land their quads.