It sounds like the DA wants to see a transcript of the DMV hearing where the officer is likely to testify regarding a driving issue pertaining to your DUI criminal case? Your case has just began. It's too early to assume the DA won't be willing to negotiate your case - and yes, there is always the possibility of a good outcome. Patience.
Her behavior and comments are unprofessional. However, they also reveal the strength of the defense. Most DA's seek verdicts in easy cases to impress their supervisors. Her outburst is an attempt to avoid a trial she fears losing. Pick 12 good jurors and beat her in trial!
I agree with the above. At the hearing on the motion, the court will likely require you to present evidence to prove you are in fact innocent and that the case was not "discharged" for witness unavailability or some other reason. You carry the burden of proof.
At trial, the jury will likely view the video tape as the best evidence in rendering a verdict. If you believe you can reasonably justify your actions on the tape and you don't feel comfortable with the plea bargain, then your only remedy is a jury trial. d