16yrs, I’m so sorry for the path you have been forced on these days. From what you have posted it seems your son witnessed you husband’s tragic death in 2006, he would have been 18 at the time.
From reading what you have shared no one can say if his problem is drugs, mental illness or a building mental breakdown from not properly processing his past but It’s for sure he is in a crisis right now. I could say to you that my son has said worse to me, but really someone who is good at hurting others says what they know is the worst thing their target would want to hear. Somehow they have that ability to say anything they know will strike an arrow through your heart, mine sure did. Your son's issues right now though are his business, your state of mind and your inner world are your issues.
Having a business to run in the middle of the chaos you are facing would be too much for me. Luckily those lines did not cross for me, so I don’t know anything of how to handle keeping employees upright and steady but maybe bringing in some overall help would be good idea at some point. And also some legal advice if you feel that’s warranted.
But most importantly, right now, it seems you are steering the ship in many ways and the rudder is melting. I think a private therapist who helps you sort out things from your perspective would be most helpful for you. The therapist I used specialized in anxiety, stress, trauma, and PTSD, she was a lifesaver for me.
I wish I could tell you how things will play out for you but really it’s mostly an inner world you move through step by step as you are ready that changes your outer world. But not necessarily the people in it so much, that’s on them to the degree they decide to work on themselves. I can say no matter what, it can get better for you, a lot better, much more balanced and peaceful. And that is what I hope for you.