i believe the water problem in ethanol is really if you let it sit for long periods.
i let mine sit for 2 weeks without moving and when i drove it agian my fuel trims were still -2, -3 right where i left them.
and the inconsistency in the amount of ethanol is not going to be by a big enough factor that your fuel trims won't be able to compensate. and for WOT AFR as long as it's tuned safely you will be fine.
if it still bothers you then you can get a device that reads the % ethanol in the fuel. all GM dealers have them it's just a simple volt meter.