Look at the first spoiler in the 3rd post in this thread about your bonus:
https://forums.ea.com/en/the-simpsons-tapped-out/discussion/90074/tips-for-new-players/p1
SH hidden bonuses can be found in the 4th table in this thread:
https://forums.ea.com/en/the-simpsons-tapped-out/discussion/81718/sh-tables/p1
On average, you will get 2 donuts per box for 1 million XP, the same as before level 939. Click on the link in my signature to find out if you should be paying to open more boxes.