I read that my Social Security will be less because I stopped working at age 63. Even if I don't start SS payments until age 70, the estimated amount is too high. For someone in the $40,000/year (inflation-adjusted) range for 40 years, is this a serious hit? Would going back to work increase my eventual SS?
Your Social Security retirement benefit rate is based on your highest 35 years of wage-indexed earnings (https://www.ssa.gov/pubs/EN-05-10070.pdf). So, the fact that you stopped work at age 63 would only cause you to receive a lower benefit rate if you would otherwise have earned more than in one of your previous 35 highest indexed earnings years.
Going back to work could increase your eventual retirement benefit rate, but only if you earn more this year or in a future year than you did in the lowest of your previous highest 35 years of indexed earnings. The maximization software available on this website permits you to enter projected future earnings, so you may want to use it to determine what effect returning to work would have on your benefit rate.