Some of your symptoms are consistent with coil failure. Search for prior threads on coil failure. If one coil (out of two) goes out, your engine will run verrrry rough, because it is operating on four cylinders instead of eight, but will allow the car to go forward. The other four cylinders will have raw unburned gas coating spark plugs, destroying catalysts (very expensive), etc. Worth checking out. Coils are easy to get to, and you can check the coil and wire easily with an ohmmeter. Email me at dickevans@aol.com if you need factory specs.