I know about the small "hobby" business and nothing being good enough for the boss.

What do you do when you are not working? Do you have any contacts in competitor/client companies of yours, belong to any professional groups? You sound like you are good at what you do and that's always valued. Is there anything you can learn from where you are (all the stuff you aren't doing enough of to suit your boss, do you ever do it to see how much you could do if you wanted or get creative thoughts on ways to help the company -- I use to read the industry magazines, for example, and think of articles I could write), what "fantasies" do you have and can you use them to help you slide into a better or more secure job?

I'm in my 60's and retired; so sorry you are where you are, I don't envy you. Good luck!