Wow.  There are a lot of family-run businesses out there and most of them have some type of family-related drama attached to working with them, but some of them aren't bad places to work.  Your situation sounds more extreme and tampering with someone's car goes way beyond the pale. 

I know you said you love your job, but it sounds like you walk on eggshells all the time.  You already know some of those people don't like you.  You feel HR wasn't honest in telling you if cameras reported someone touching your car.  It sounds like things could eventually escalate into something bigger whether you love your job or not.

Based on what you said, I would be pro-active and start looking at other opportunities now.  Hoping you find something you really like.