Do I have a case

I worked for a national respiratory company for just over 5 years. I was intially hired as a sales rep (and signed a non-compete) but assumed the role of manager within the first few months of employment. My pay and title officially changed to manager after 3 years of employment. During this time I consistently received good performance reviews and I exceeded the sales quotas set for my location. At the beginning of the 4th year I hired a sales rep to assist, the sales rep worked for our company for about 1 year and was fired for a medicare violation. Immediately after the sales rep was fired my manager called me in and suggested I step down and resume the sales position at more than a 50% cut in pay. I repeatedly refused over a period of 3 hours. At which point she pulled a sheet of paper out and informed me that I was being written up for not preventing employees under my supervision from arguing among themselves about the sales rep termination. I told my manager that I felt that one of my staff was involved in an inappropriate relationship with a manager from another location and that my staff and I had witnessed her on long phone conversations with this person. I told her I felt that this staff member was causing the discord. My manager told me that she had also heard the rumor but would not be doing anything about it. She then informed me that I could be termed at anytime due to any perceived retaliation against the staff (I had never done this). The next day I recorded a phone conversation of the employee I had accused and the manager from another location and it was apparent that they were consipiring to report me for retaliation so that I would be fired. I wrote my resignation and forwarded it to HR and I requested an investigation. I have been denied unemployment benefits. Do I have a case against my former employer? or do I have a chance of winning an appeal of redetermination of benefits for my unemployment?