Weird gas station happenings

[Dantak]

I went to the tank the other day and started filling up. As usual, the handle kept reseting. I knew it wasn't empty so I kept fiddling around with it until it stayed on. Then locked it on the lowest setting. After I hit 11 gallons, I thot "that's weird and looked under tank for a leak. I didn't see anything. I stood back up and looked at the pump and it said 15 gallons. Wow, I grabbed the nozzle and pulled it off and fuel started shooting out of my tank. So needless to say, I over filled my gas tank and it expanded like a fuel filled balloon and then shot gas all over the pavement. I've thot long and hard about this and I can't figure out how the nozzle made a liquid tight seal on my gas tank or why the nozzle didn't shut off. I've given up figuring that out, the weird thing is, my gauge is off now. When I fill up it says barely more than half a tank. I suspect it will say empty when I hit about 120 miles when I normally get about 170. Any ideas on how I screwed up my guage and how i can fix it?