So the pull over he did is at MINIMUM against department policy and borderline illegal. You have to have a LEGAL reason to stop a car and just a “feeling” or “because he wanted to” are not valid reasons.

The dash cam is the best idea but get one that films outside the front window and the interior of your car and make sure it records audio too.

Most likely the Sheriff is an elected position and will take this serious BUT I think your best protection is to reach out to local news with your story. First off it should get the deputy to back off because it’s now public, and second force the Sheriff to do something since as I said above they are elected and will protect themselves so they don’t lose come re-election time.

The news is probably your best friend because taking the story out of the dark and into the light will protect you because you are now known and her ex (hopefully) will go away.