As a teacher, I need to caution you to not discuss specific student cases on the internet, no matter how anonymous this seems.

I hear and understand your frustrations and fears. Making threats against individuals can and should be reported to authorities. Personally, I would not work under those circumstances. There should be a Spanish-speaking adult involved at all times; that alone would curb the language-based issues. There should be charges pressed for any physical assaults. If the district won't back you on this, get out. You can't fix this on your own, and if the district isn't willing to do what needs to be done, this is not a situation you should stay in for your own safety and well-being.