I am very sorry about your situation. I’m afraid you cannot control MS attacks by willpower, or any other method. The only things that have shown modest success are disease modifying drugs (DMDs), but I do not know if you are eligible, or even want to try them - especially as there is a possibility of side-effects - particularly in the early days, although these tend to reduce. You may not feel drug side-effects is something you can live with at the moment, given how much else you have on your plate.
Vitamin D may have some protective effects against relapse, so I recommend to take a good supplement, whether or not you’ve been found to be clinically deficient. You have to take extremely high amounts to overdose, so it wouldn’t hurt you to supplement anyway, even if you weren’t deficient. And they’re pretty cheap!
I don’t think it’s possible to guarantee a relapse-free nine months, even with the most powerful current DMDs. So the crucial thing is not so much prevention, but to have a really sound plan in place in case it does happen.
Is your doctor aware of your situation - that your wife is terminally ill, and you yourself have MS, and could be taken ill with very little notice?
I’m sure care for your wife could be arranged, in an emergency, but it may be wise to discuss it up-front, so you know what the plan would be, instead of waiting for it to happen. This could give you some peace of mind.
As for being “on your own” with MS - this is a worry at any age - not just at 65. I live alone, and do worry - I’m 48.
But I’ve been diagnosed about four-and-a-half years - probably had it many years before that - and have so far never had a relapse that was instantly incapacitating, to the extent I wouldn’t even be able to call for help. It doesn’t tend to be like heart attack or stroke.
But you could ask your doctor about one those emergency SOS bleepers you can wear round your neck. I’m not sure if there’s a charge for them, but if there is, I don’t think it’s huge.
I’ve wondered about getting one for myself, but as I’ve never fallen or been completely incapacitated, I wonder if that’s being a bit paranoid. But if I was the carer for another person, I probably would. It’s OK to take a gamble with your own safety, but not with somebody else’s. Ask the doc about that AND emergency care arrangements.
All being well, you won’t have a relapse, and it won’t arise. I haven’t had one for years, despite doing nothing special about it (except the Vitamin D). I certainly think it’s luck, rather than technique, but it is possible to go a long time without relapse, so you might be fine.