The judge should check to see if the officer meets the calibration requirements of their radar if radar was used to determine that you were speeding. Click it or ticket allows officers to pull over drivers they suspect are not using seatbelts.
Does this vehicle have shoulder belts? If not, then perhaps that's why the officer pulled you over. I do not think that click it or ticket requires signs for enforcement.
Do go to court, but leave your anger/emotion at home. Judges see people every day and they already have a way they handle cases like this. Bring in pictures of the car, proof that it uses bio-diesel, a note from a long time mechanic, evidence that you just pulled out of that establishment (receipt). The judge may or may not accept any of this evidence, but you should be prepared to offer it as requested.
Judge Wapner did take a drive in a plaintiff's old car once...the ride convinced him that it was impossible for the car to be going 85 mpg or whatever he was accused of. So, I'd bring the car along, too!
NOTE: if the judge already has a plan, it'll likely be a reduced fine and no points. No points is the IMPORTANT PART. Points makes your car insurance go up. Take the reduced fine is that's what you are offered after explaining your case.
BTW, I'm much more likely to speed if I'm feeling stressed/rushed. How were you feeling when you left that establishment? Where were you heading? I'd return to the scene and see if you can recreate the situation - you may be surprised that 45 is easy to hit when you are feeling that way.