Here's the bad news: You can't magically make bad gas into good stuff. Once you've got a tankful, you either have to pump it out and discard it, or live with it.
I'm not sure I like the advice (but maybe its good) of just adding good stuff to the bad. You might end up doing that for a week or two, and still have it running like crap.
What most of us do is first, go back to the favorite station and speak with the manager. Talking to the clerk is a waste of time, and they had nothing to do with it. But if others are complaining, too, you can be sure of the source. Then fill a 5 gallon can with assumed good fuel, from another station. Pack up the family and take an extended drive at highway speed. Its easier and cheaper than trying to pump it out and finding a place to discard it.
Only use the good fuel if it gets so bad you can't drive on it. Chances are a few hundred miles (and a few hours, like 5 or 6) you can run it down to below a quarter tank. Then fill it with good stuff from a station out on the interstate (heavily traveled, so high turnover in the tank.) I'd run premium, just to get the extra alcohol to dilute any water if thats the problem.