If you think you've been targeted or "gangstalked" at work, what steps did you take to protect yourself and secure your employment?

If possible secretly record at the very least audio. They will workplace mob you. And them knowing they are being recorded will reduce the harassment somewhat. Keep written documentation as much as you can. The purpose of the mobbing is so you quit or get fired from reacting to them. Try to hang in there and do not quit.
If later you are out of work consider healthy volunteer clinical work: TIs in need of work, try clinical trials