You might want to look into how your pension plan works. If you leave, you should be able to either A) Leave in the portion that you've contributed to so far, and get a partial pension when you retire or B) cash in the plan value and self-manage it. They normally can't just take away your pension when you leave, or just refund your contributions. You should be entitled to anything you contributed to the plan plus whatever interest it has made on investments.

I left my job of 22 years because it was destroying my mental and physical health. My grandfather died on the day he retired, and my father died 1.5 years after he retired. No way was I going to take that chance. No pension is worth your health.