Thanks, Uatu. I figured that some of my questions were going to be resolved in Unearthed Arcana.
Some of the issues are just additional information, but some are typos, e.g. the correct max level for assassins.
I'm going to assume that the answers to all of my questions were from Unearthed Arcana.
So, when I'm done with the Player's Manual, I'll go to that book next, instead of to the Dungeon Master's Guide as I had planned.