Should I reroute my condensate line to prevent freezing?
With my furnace, I diverted the drain line into a 5 gallon bucket which I used to flush toilets.  You could install a wye and a valve or two to make the condensate drain into a bucket inside the house on the coldest days. This may be a little too high efficiency, Worked for me.  The tricky part is remembering to check the bucket.