Wait a min guys dont scare him. Nothing will happen bro , i had got similar situation. The only difference is that u stopped and got hit and i didn't stop  and got hit. I was little bit lucky than u that the car was backing up and i thot its not necessary to stop and i didn't stop though the exam taker said and i got hit. He called cops and gave me 250 bucks normal tickets on careless driving, there was normal court date of two month as like yours but i paid it before that so i didn't went for date and nothing else.  Its just simple case of an accident which ur insurance will take care. On mine i made them to pay though i paid for ticket. 
Of course there is your fault but not as much as u should be punished so bad ! You can go court and fight but there is no chances of yours to be safe since its all ur fault to not to stop on sign. 
If you are thinking to be safe because you were taking test and sombody screemed than forget that, even though you were taking test or not , its your fault to not to stop at Stop sign. 
good luck. i don't think you need layer too unless you are planning to fight case which has clear chances of loss.