Engine Shut Off Without Warning problems of the 2007 Honda Civic Hybrid

I am the original owner, a conservative driver, rarely exceeding 60 mph to increase mileage, and drive for work in an area east of dallas, texas. I had great mileage and no problems to speak of until this past June. I first had noticed a deterioration in the gas mileage. Then I experienced for the first time a drastic drop in responsiveness. I was entering a hwy from a country road and found myself with no power. This has remained so despite the software update. The number of bars showing on the gauge was significantly fewer, and there would be wild fluctuations of bars. There has been no warning light. I've had several conversations with the dealer. Mailed american Honda a complaint, resulting in a call from Honda that seemed to me simply a way to mollify. Honda apparently does not consider this problem a "safety" issue. I beg to differ. Now I must always be aware that I don't have power (the cooler weather has generally seen a higher number of bars), and mileage has definitely suffered. One clear example is that since the software update, the gas engine does not shut off as much as it used to, especially during hot weather. If the engine shuts off at a stop, it also can abruptly engage again without warning (nothing changed such as brake pedal pressure, etc that would cause the engine to come on). I bought the car to be a 10 year, 300,000 mile product, with no concern for resale value at the end. Now I'm paralyzed with the prospect of poor resale value, perhaps unable to sell privately - restricted to only the dealership. This was the first time to buy a Honda - based on a reputation for durability.