This range of responses have been fascinating - thank you, especially to the people whose frustration I can read but managed to remain polite and not say things like 'use your words like a big girl.'
I'm afraid I am so frustrated at this point with recent updates I didn't even want to post them, but this is the reality of our situation.
DH called IL's prepared to have an honest discussion. By the time MIL grumpily got on the phone, he cowered. He stood by the lie he gave GMIL and told her we couldn't go because of work. She asked him to try and come before March to have this 'family dinner' while AIL was still in the country. He hung up, walked in the living room and said 'so...do you think we should go?'
Well. My head about exploded. I told him I needed time to respond to him because right then I was too angry and frankly confused and frustrated. A few days, and one large argument between us later, DH has now written actual notes down on paper, with categories, and is going to call his mother tonight and try again to have, what he hopes, will be an honest discussion about what happened and how he'd like their relationship to improve so all this nonesense stops.
I can't tell you how frustrating it is to see my handsome partner, so strong and confident (an executive financial CFO who manages hundreds of millions of dollars and staff), turn into ...well, the above, when dealing with his mom. Behind all this etiquette mess are absolutely deeper rooted issues he has to deal with.
We're not going. That is for sure (even if we wanted to at this point we can't due to work leave no longer being available). I think at this point the only thing that can be done is an honest discussion, and an attempt at addressing some of these larger issues.