I've made the update for 1 as you suggested.
For 2, I'm not sure how to make it clearer. The imports are repeated because they need to be in two different files. First I'm talking about your controller file(s). The second is talking about adding a GRID_DEFAULTS variable to your common.py. To do so you need the imports again.
I made a change to specify the controller file(s) on the first mention of the imports. Let me know if you have a better suggestion.
-Jim