Wow, somehow I got 47 out of 50, but I did guess on a few more. Questions I missed: #4 (newspaper/national pastime), #33 (I had no idea where Scully went to college) and #44 (total number of perfect games).
Questions I guessed correctly: #16 (only catcher to catch four no-hitters) #31 (only player to hit 50+ home runs and strike out fewer than 50 times) and #35 (only player to win ROY, MVP and Cy Young).
Most of the first 30 questions were pre-WWII stuff, and I've read up quite a bit on the era from ~1903-WWII.