Just going back to the original topic of this thread, I would say that my pre-heating the pool by running my pool heater in advance of this weather system has helped. I am in Oklahoma City where our temps have been a good 10 degrees or so below yours throughout this event. I had the pool at 70 when we went below freezing on Friday night. As of this morning, I am at water temp of 37 (air temp was at 3 overnight), which is a little higher than you after a longer period of temps that are quite a bit lower than yours. I estimated earlier that heating to 70 in advance bought me about a day and a half additional time before reaching 32 degrees. I think it might be even more than that given what you guys are saying about your temps in Texas.
Just for context our temps here were in the single digits for two solid days. We are just now going to get into the 20s during the day today, and then to the 40s tomorrow.
That said, we also had a good bit of sun throughout, only a little precip, and not a ton of wind. The impact of this event seemed more mild than the one we had last Christmas, even though that one was shorter, I believe.