Yes, at age 55 you should be able to bank a bunch of cash by jumping to a legacy.

Exact amount as Fangs said depends on contractual nuances, and relative seniority and availability of flying in specific base and seat.

But in this climate you might not get multiple CJO's in short order, might have to take the first one that calls. If you do have a choice, and are geo-flexible obviously take the one that has a junior base that you're willing or prefer to live in. You can always make more if you live in base and can pick up and trade last-minute.