Painter's Ladder Shelf

HELP! I am trying to build the painter's ladder shelf. I am having 2 problems.

First, my legs keep splitting when I screw the pocket holes in and then there doesn't seem to be enough wood left for the screws of the top to grasp. Does that make sense?

Second, I noticed that all of my shelves are 1/8th off on one end. Is it possible for my miter saw to be off square? How would I fix that?

Thanks for your help.