By continuing to let this person into your life, it is damaging you mentally further and further. You cannot be on disability, so this job is your life line. Do you see where I am going here? He will be back. He is in a homeless shelter. He is going to want money and shelter. You must prepare for that.
Look, I get it. There have been days I don't know how I drug myself to work. However, I know with 100% certainty that my chaos will go from bad to much, much worse if I were to lose my job. So, I make myself go. I did the best I could. It was a reprieve sometimes to get my mind off of other things.
You can do this. I see how productive you can be when you set your mind to it. We are here to support you, you are not alone.