The A419 has an anti-short-cycle function that should ensure you don't cook your compressor. It can be set as long as 12 minutes. You probably should look into that.
As for the large differential and even larger apparent temperature swings, the latter is likely due to where the temperature probe is located, and the former was set to cope with the latter (maybe?)
Keezers (and fridges to a lesser extent) will see the interior air temperature drop below any set point, due to the nature of the cooling mechanism: the compressor shuts off at the set point, but the expansion coil is still filled with working fluid changing to vapor and thus extracting more thermal energy until equilibrium is reached. If your temperature probe is hanging in free air it will "see" all of that. Otoh, if your probe is attached to a large thermal mass inside the keezer/fridge, the swing it sees will be significantly narrower.
I run two fridges and a keezer with external controllers, typically with only a degree or two of differential, by coupling the controllers as tightly as possible to what I'm actually trying to control: the beer.
For my fermenting fridge, I stick the probe against the carboy, slap a 1" thick chunk of foam insulation over it, and crank them down tight with a velcro strap. For my carb/cold holding fridge and my keezer, I do the same thing against full kegs. The result is infrequent cycling and brews held within a degree of where I want them to be...