I live in PA which is an at will state and was recently terminated from my position without reasoning

How likely is it that something could come of this. I was terminated yesterday without warning and I live in Pennsylvania and am under an at will contract. I believe laws were violated because the director shorted my pay and I escalated it and then yesterday was fired. The issue of my pay was resolved in my termination letter. To give more details, for the past few months I’ve additionally experienced bullying and basically shunned by him. He would never acknowledge me when I spoke to him or answer my emails. It would take several escalations for me to get a response and all cases were in regard to my job duties. In addition, I have never received negative feedback during my one to one meetings and fulfilled all of my job duties. He additionally in the past has requested me to perform unethical duties in regards to a grant- he told me to sign sensitive documents for participants (under 18) with verbal consent over the phone. I refused to do this and it escalated. He additionally has requested me to contact our participants schools for their report cards without a release of information. I worked in a non profit organization for youth interested in pursuing stem programs. After I refused several times, it escalated again. Both times he was verbally aggressive. I am going to file for unemployment today because when I asked for a reason for my termination, they said “as you’re under an at will contract we are not required to provide reasoning.” There was no indication of this firing and I am not sure I understand my rights here. What can I do. I’m sorry if this is all over the place, I’ll be more than happy to provide more details I just don’t know what is important or not right now.

Location: Pennsylvania