Retaliation

I was terminated from a local employer, for what was listed as poor performance. In my termination letter it states three discussions in a six week period (never happened, No documentation). Three weeks prior to being terminated, I received a signed and dated thank you note from my supervisor (same one that fired me)thanking me for the job I had done and stating I was the best person for the job.
Thursday before my termination, another director physically threatened me and stated he did not care to lose his job, it would be worth it to kick my *ss, along with some other brilliant comments, and getting up and coming at me. I called administration and complained, the sent me home saying I was upset and needed a break, even though I asked to stay at work. The other director stayed at work. I filed a complaint with HR about the physical threat and sent an email to the HR Director about the incident and that I did not feel safe. Monday, when I returned to work I was terminated. I was not allowed to view complaints that he had supposedly collected about me, during the past months.
The supervisor is also telling several stories about why I was terminated, that he did not list on the termination letter. I have had several people that still work there call me and they are sick of what they believe are lies against me.
I was told I need to start fair practice process, by HR, I was told that I need to state what I would like to receive, reinstatement or monetary, I have accepted another job that pays less. Can I sue after arbitration? Should I contact OHSA under safe work enviroment? How much should I ask for?
If I would go back to work there, he would simple spend his working day trying to find a reason to fire me.