I was 65 when I had my mandiblecomy. not a fun ride but certainly easier than my cancer treatments. Went on a feeding tube for about three weeks and received my teeth prosthetic about ten months later. I was eating before the feeding tube came out. All in all not too much trouble. But I do understand the reluctance with the MS as it certainly will trigger issues. My wife has relapsing remitting MS and it doesn't take much to send her over the physical edge.
Without the surgery, it will not get better and likely worse. If the bone breaks, then it is an emergency situation that most local facilitates are ill equipped to handle. I think the good doctors up at Mayo Rochester would think your age does not limit you. The surgery is an eight hour day +/- and the recovery in hospital is roughly five days. There is some work-up appointments prior to surgery but that is all fairly easy. Courage.