So, obviously the W163s have lots of fuel tank and sensor related issues, and as much as I would like to believe that its only my gas cap that is screwed up, I am a realist . So here's my story, and I hope someone can tell me what is most likely wrong with my vehicle. This is a two part question:

I was driving down the highway a week and a half ago, when I felt a sort of bumping up and down, and before I could even pull over, it stopped. I kept driving trying to figure out what it was, when all of a sudden the car started vibrating wildly and slowed down very quick, the ESP came on and everything...I pulled over immediately and noticed one of my tires (rear, driver's side) bouncing down the freeway. Oh man.

Luckily nobody was hurt. So anyway, I shook it off, changed to the spare (and noticed the vibrating knocked two of the three plastic bumper cover panels off...thanks, Tire), got back in and started driving again. This is the first part of my question. The ESP came on and starting going bonkers. Is that a common occurrence when putting on a spare? I suspect it was sensing the tire was slipping as it got seated properly on the lug nuts. Anyways, it stopped eventually.

Then, when I got to where I was going, my empty fuel warning light started flashing. I used context clues, and unscrewed and reattached the gas cap, with no further lights of any kind. Fast forward to today. I was driving and the gas light began blinking again, this time carrying a check engine light. I swear to God, that light has been the source of my anger and hatred for the past two years. Anyway, I parked, shut it off, did the dance with the gas cap again (twice) and the blinking gas light went off, but the Check Engine light is still on. I cannot rest until it is gone again.

After analyzing the facts, what is most likely wrong with my vehicle? Thanks for any input.