Temp control with Dayton controller

So I bought a 7cu. ft chest freezer this summer so I can control my fermentation temp. My dad had an old analog Dayton controller lying around for me to use. I placed one of those portable weather stations to see what the temperature differential was, and setting it at 58F seems to give me 57F to 72F range.

From what I gather on here, 15F is a huge temp swing for a controller. I'm not sure if I want to use it like so and hope that active fermentation, along with the probe not being near the fermenter, mitigate the temp. swing of the wort.

Thoughts?

A 15 degree differential is a lot. Is there any adjustment anywhere on the unit? If not, then you could set it so your desired temperature is halfway between the extremes of the differential range and see if it maintains that average temperature. Even with a large swing, with thermal mass it may settle in at the desired temperature. Test it that way if you can...