It's almost identical to my brother and dynamic with mother shit stirrer matriarch.
It's been hard but I did spell out to my mum this week, kindly, that I needed space because certain behaviour I was experiencing was not ok and crossing multiple boundaries. I haven't heard since. That's kind of what I need. I sent kisses. I really want to say fuck you but it's a game in some ways.
I don't know if you feel that would help get some of the message across for you.
I've been really good at NC with bro and haven't faltered because the peace I've had made it clear to me how much he needed removal. Sadly, mother has been trying multiple attempts to manipulate, hurt me and re introduce him into my life and my child's. That's when I said no way and spelled things out. Sometimes we must clearly spell out our boundaries to make that break.
I agree that grey rock is hard if they don't stop, there's more than one of them. It's too much.
I'd re watch some videos or advice online from professionals on these narcissistic family systems to help re enforce your resolve and remind you how damaging their contact with you is to your life.
I always recommend Dr Ramani.
We have been trained all our life so reacting is a natural response. Learning to hide it from them and pretend really helps. I noticed when I didn't hear from brother after NC how I became more and more indifferent. That's the aim. The minute my mum started trying to re introduce this it brought everything back and I've been highly reactive again. That's why distancing them entirely is often the ultimate goal if possible.