A: Yes. Evidence can be admitted by way of video or verbal testimony. Therefore, the officers involved in the traffic stop could simply testify to what took place (what they observed) and it would be up to the judge or jury to determine if that verbal testimony is credible. As you might imagine, video evidence would make for a stronger case but is not a requirement to convict.
A: Not quite sure that I understand your question. That being said, if you charged with a crime while on probation. The new charge(s) will trigger a probation violation which is a separate issue that you will have to resolve in addition to those new charge(s). Furthermore, if you are in custody for 90 on those new charges without being indicted, you are entitled to a reasonable bond for the new charges only -- Not the probation violation. This is true, even if the new charges caused the probation violation.
A: Technical violations carry up to two years in prison -- if a defendant is revoked. The fact that prisons are crowded is generally not a factor that the courts consider in determining a defendant's sentence. Your best move is to hire a good criminal defense attorney or seek the services of the public defender's office to advocate on your fiancé's behalf. The more serious the underlying charge, the more likely that the prosecutor will recommend time. Good luck