Take a look at your KR values in your logs as well. And if you haven't already, check the knock sensor wires for chafing. If you have E85 available, try and add a few gallons to your next tank, as it will raise your octane level. Those two things can help to raise the OAR/confirm it is gas.
The Knock sensors wire chafing would lead to OAR closer to 0, due to false knock readings. This would have nothing to do with your gas, and would persist with non-winter blends.
Adding E85 would ideally bring your OAR closer to -1 from where it is now. If this happened, then you would know more definitively that gas is to blame here.
Winter gas sucks. That said, my OAR only ever got as bad as -.76 when I had my E20 Tune from AJP. There were points in winter when it was below freezing out, and I had -1 OAR and > 20 degrees of spark advance. I only ever ran Shell 93 (which is an E10 blend) and then got E85 where I could. ~3 gallons of E85 to the rest of the tank of Shell 93 V-power.
OH, also, the colder it is, the more fuel you need to get up and running until the car is warmed, and in some cases over all. AJP and I went back and forth with some datalogs the first winter I was tuned, and fattened up my fueling a bit. In the winter it kept me running as close to commanded/stoich as we could get. In the warmer weather this tune ran a little fat/rich but that added some slight safety.