Update: this issue turned out not to be related to the ABS/ESC at all. The jerking was being caused by small misfires. These misfires were detected in OBDeleven, but not significant enough to store any pending or hard codes (weird). The cause: my filter came loose and fell off inside my APR box. Since reconnecting the filter, I have not had any issues thusfar with jerking, especially in blowing snow. I think snow was contacting the MAF, interfering with its operation.
Slightly embarrassing, but still a good learning experience about how to distinguish misfires from other issues.