Awe Grandma J,
I am sorry you have been going through this, it is awful when you have created a family business that your children will be able to carry on for you, and then to have fractures within the relationship, affects every aspect of your life, not just work, but family as well.
It sounds to me, that your son is in the wrong; the only real advice I can give you, is 1) Treat him as a professional like you would with any employee, and just at the moment, separate the fact that this is your child, at least when you are at work. Any employee has to have a professional conduct and that means coming to work on time, and sober, so once things have cooled off, you may have an opportunity to sit with him, and reason that he has not been the best employee lately; not measured by his productivity, but his attitude.
2) Only apologize for your reaction, and for words that came out which hold no truth. We have to live with ourselves, and as long as your conscious is clear that you have said sorry for your reaction, you can do little else to change him. I know these are really hard words to say when the other person is in the wrong, but you will gain peace of mind that you have humbled yourself, and if he holds onto things, that’s his choice, not yours.
My other thoughts though are; can the business still be a success if he does walk away? (That would be one of the choices he has) Can someone else do the job which he has been doing? And, really, can you hand the business over to him at the moment, and trust that he will honour and serve the current customers that you have built up over the years? It may not be the best time for you to do this, as he appears to be on a spiral at the moment.
Your Hubby had some great advice, but sometimes the gift of time, makes things harder to heal, so before things get any worse than they are I would be trying to find a working solution as soon as possible; not for him, but for you, I can see that this has devastated you, and you are right to feel that this is unjustified, so I am only concerned with yours and your Husbands sanity.
Please let us know what has happened after going into work today; please be gentle with you Grandma J