You've shot yourself in the foot pretty thoroughly. There is no necessity defense here. If your car was in such poor shape that you had to speed to avoid harm to yourself or others, the proper course of action is to get it fixed before taking it out on the road. The officer will testify regarding your statements during the stop, further torpedoing your case.
None of your minor things are going to get you anywhere. The weather and color of your car are to an extent subjective, especially when neither is a factor in your infraction. The $190 likely includes court costs and other add-ons above the legally mandated $78.
Your best bet, since you subpoenaed the officer, is to try speaking to the prosecutor before trial to see if they are willing to cut a deal with you to amend it to something non-moving. Bringing proof you fixed the car would probably help your case.

