MUTCD Federal manual for traffic law the guide lines are clear that speed limits determined by city or state engineers conducting radar survey of traffic on flat level stretch of road. I was traveling down hill with the officer below when he claims his radar clocked me at 90mph. I was a head of 7 cars after coming a round the front two from previous passing lane and hit resume on cruise control which was previously set at 70 mph
90 > 70 > 65.
You were speeding. You got caught speeding. The posted speed limit is the speed limit, even if you are going down hill and are in the passing lane, actively passing cars.
1) You need a lawyer. Your defense, as expressed here, is not going to help you, so you need a professional to speak on your behalf.
2) Next time rent a car for your trip. That way, if the car breaks down, the rental place will bring out a working replacement to you.