The best course of action would be to have either your fiance, father or a male friend accompany you to the barn at least once, but preferably routinely. Steel toes and a knife are effective deterrents once they come into play, but the situation needs to escalate to a pretty high level of severity to make any use of them. The BO does not respect you, you're not a tenant or a trainer, you're a sexual object he desires. You've shown him that you can be pushed around and bullied already (no offense). It will take a lot to change the perception he has of you, a lot. Just introducing an intimidating, preferably male, presence would go a long way.