Apply for the same position where there are more Caucasians, in the same educational institution, hopefully, in a location closer to home,

You can report the racism, but it risks employers seeing you as a trouble maker.

"Then he got brave enough to call me a F B the very next day, got suspended for a few days and everything is hush hush now"

That incident is grounds enough to justify wearing body a cam and recording.
Document, document, document.

But, also, lay out the guidelines for grades...and if work/testing falls short ...give the appropriate grade.
Don't you dare cower or chicken out.
Grades are meaningless unless there are solid metrics behind them.
You are actually cheating the other students if you pass someone who should have been failed.

Keep writing the stuff down and at some point go higher up in the company and present your findings. If that don't work, then seek other employment or hire a lawyer. That's not right how they treat you. This is the 21st century, not the 19th.

Well, some good news; Being an Agnostic/Atheist makes you a bone fide minority for "religious" classification. Something to keep in mind for battling charges of "racism".

Meantime, I think you are doing right by not acknowledging such issues and documenting the facts of infractions and corrective action as objectively as you can.

In your place, I would stay with it, continue doing as you have been and respond appropriately and calmly to any questions or challenges. Don't chase yourself out of there for them. Force them to do that by being reasonable and document the facts of the matter as best you can.

If you are treated unfairly, contact a lawyer. It may not do any harm to introduce yourself to a Civil Rights Attny right away anyway just to establish contact and get good legal guidance when you need it.

If you can, record and document. After you do that, go back to HR (or whoever you talked to the first time) and play the recording and show your documentation. If they still won't do anything file a complaint with the EEOC. Another alternative is to go to the media with all your evidence, however that could bite you in the ass.

I would also keep looking for another job.

So when you went to the supervisor he said you're gunnysacking, but then said he can't do anything? So why would he think you would go to him again? Did you bring one issue to him or numerous? What racist thing actually happened that you claimed?

I can’t say what you should do but what I would do in that situation is stay cool, start looking for another job, not necessarily with the intention of taking it but as a backup so you can negotiate from a position of power, or to fall back on if things go south. Then I would try to make a friend, to have an ally there, and then make another. Meanwhile I’d take it all as a challenge, do the best I could do with the bad situation, and not worry about the outcome because I had made every reasonable effort to cover all my bases while being fair and humane to all others concerned.
If another job comes through that actually looks more appealing... I’d be gone! If things start to turn around before a better job shows up... I’d feel triumphant, but I’d prolly still keep an eye on the job market; that really sounds like a permanently stressful environment.

Being Hispanic... I can say I had received more racism from blacks than of whites despite my non white skin color. I had to live outside of usa to learn that races are not colored!!! You have to be True to Yourself. To think that a "minority" in this country will not use numbers to his/her advantage when available is pretty Naive. Go with your Conscience. Keep a ledger, document everything. I know is a Tough Spot for you because the "minority" in your workplace rather have another "minority" in your place. Like sharks... if they smell blood in the water... they will feel empowered!!! Give the grades they deserve. Found another place to work... this is about You and should be about You. Nobody else is going to look out for you and america in all different manifestations, still sucks. Find a better place to work. And wishing you the Best of Lucks.

As others have advised.. the most likely path to being happier will likely require you to find a different job. In the mean time, don't give up, with time a different path will likely open itself up to you.. it could even be as something as simple as you need to be there a certain length of time before your accepted.