Chest Freezer with temp control question

I am using a GE 5.0cu/ft chest freezer with a Johnson Controls temperature control.

Question 1: the chest freezer has a temperature control on the outside, should I set this to the highest (coldest) setting?

Question 2: the freezer is in my garage, i have a standard two plug outlet. Both plug outlets are being used. I run an extension cord to my water cooler next to the freezer. Can I just run a splitter off the extension cord to run both the water cooler and freezer? Or am I creating a fire hazard?

1) Yep.

2) It should be fine. The specific answer to this question is that you need to know how much current the freezer and the water cooler draw, and then make sure that you use an extension cord that is properly rated for the sum of the two current values.