2012 Ford Fusion car problems

Hello, I am an owner of a 2012 Ford Fusion that I just got a couple of weeks ago. Last week I mixed regular unleaded gas with ethanol. It was jerking when I would stop & take off. One morning it was jerking bad and it wouldnt accelerate. My uncle did something to where it can accelerate again. So everyone told me to run the gas out & just put ethanol in it since it says Flex Fuel. Today I had 17 miles left until it was on E. I was at a stop light & the car battery light came on and it shut off. It did this five more times until I got to the gas station. I put the right gas in (ethanol) and thought it would stop. It kept doing it. It happens when im slowing down like at a stop sign or stop light. And yesterday when I started the car all the lights kept flashing. Then it said "Check break system" after but I ignored it. Is this a serious problem or something easy that can be fixed?