If I were in your shoes, first thing I'd do is look for another job. It's much easier to negotiate better pay when you still have a job. If you're pirated, you can even ask for a signing bonus equivalent to the retirement pay you would've gotten with your current firm. Start by maximizing your network - ask friends in other companies if they can hook you up with any openings. LinkedIn is also good but it's better if the recruiter reaches out to you rather than the other way around.
At the same time, make sure to have your butt covered with all the email trails. What you'll be arguing if ever you get terminated is unjust termination. Not that you'll pick a fight and make the first move, but if it happens, you're ready.
Don't be the first to resign unless you have a better offer. Surely if you've made it through 15 years, a couple more months won't hurt you. Resigning without a new job to jump to is like throwing in the towel and letting them win. Don't give them that victory.
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