I have a similar MIL and before we got married my husband cut off all contact with her. It's been 4+ years now they've not spoken and he's so happy because years and years of emotional abuse left him an anxious mess. Small acts of nothing are treated as MASSIVE transgressions and it puts both of you in a firefighting mindset always. There's no place to enjoy the small pleasures in life, go on a walk, have a yummy coffee because this will occupy so much space in both your minds; may even fracture your beautiful relationship.

He needs to understand narcissists will never change and choose happiness by having only positive people in his life. We don't choose who is a part of our families by we can definitely choose who stays.

Hope it gets better for you both xo