If your mother is this psycho to you and your sister, it’s likely that she’s that way to the rest of the family too. Bypass her and have good relationships directly with them; if they’re normal, they probably know to treat you the way you are rather than the way your mother says you are.
And for that reason, it might be worthwhile to reach out to anyone you are particularly close to, and have an excuse to get together. Host a cousin BBQ. Meet your favorite cousin in a bar. Don’t make the point of the occasion making excuses, but if the topic comes up say “Mom’s always been nuts - if anything wife has always encouraged me to keep that door open - I’d have shut it long before now if not for wife.”
If you aren’t close enough to any of your cousins, aunts or uncles to call someone up for lunch or a drink, you aren’t close enough for your wife to need to care.
Thanks again everyone.
I think I’m going to avoid a giant email - as many of you said, it’s just stirring up more trouble I don’t need.
I am going to take Dangerosa’s suggestion of planning more activities with various family members. The rest of the family is a bunch of good people; I should be spending more time with them anyway.