[Snipesy]

The EPA (which is what your cruze is made to) allows some grace with frozen DEF. As long as the heater is working (hah!) it should be fine.

Also in my experience if the def is frozen it will jump to around 33% or so,

 

[Snipesy]

I think the 70 minute rule is just for the EPA's testing. I doubt there is a 70 minute death clock built in, but I could very well be wrong.