FMLA, demotion upon return, hostility and now Mutual Separation document

I had Spinal Surgery in August. We just won several contracts so I tried to get back ASAP. Well after a week and a half I went back but couldn't focus. On that Friday my employee got HR in a call with me and was extremely disrespectful, nasty, personal, aggressive and completely unprofessional about my health issues. After that my HR Manager said she was completely shocked by the complete verbal assault on me and we said we would discipline the employee on Monday. Over the weekend I realized that the reason I couldnt focus had been because I was having a stroke in my eye. I initially lost 40% sight in my left eye by my nose. I literalky had to take several months for my brain to reprogram and accommodate for the loss in order for me to read for 9+hours a day. I was under FMLA and Short Term Disability. When I came back after 4 months I was told there was a reorg and I was no longer the Recruiting Manager but Recruiting Lead and now I reported to the HR director. I asked about the disci