I vowed 3 things when I got married. I agreed with the rest but wrote my own as add ons. I vowed to stay his wife (and I will), his lover (he will always be loved), and his friend. None of that is in the ultimatum - only what I will watch and live with and only then if it has become his choice not to get well.
I've no regret - I would marry him again tomorrow. Love is not need, he has all my love but I don't need him so much that I'll put myself through the torture of watching regardless of his choices.
If we split - I believe he would come back. He's still my soulmate and I think I'm his. My life would go on and be full but unlike the last time I let him go, this time I'd smile to myself knowing he's full of surprises!