Hello GoodMom
Welcome to the community I'm sorry what brings you here though glad you've joined us for support and learning with us. Parents here dealing with the devastating behaviours you are experiencing from your son and his threats to keep grandchildren from you, I'd be heartbroken in your situation. We love our children. You've been through so much, second time around and you always do your very best, that's what we do here.
Are you conversant with the tools and lessons to your right

you mention managing your reactions, 'don't react, respond with S.E.T may help you, let us know what you think.
GM is your son aware of his disorder, how is his wife coping.
I joined bpdfamily 2 years ago and have never looked back, forwards we go together, small gentle steps

WDx