I'm sorry to hear you are both in such a difficult situation but I really don't think 20 pages detailing all the problems is going to help. You need to focus in on the important points, so I'd say you should file that away but don't share it with people.
The 20+ pages was the idea of a friend, I wanted to respond to the last email (and it wouldn't have been polite), a friend told me to write about everything from first meeting Mary, all the good and bad experiences, then go through the telephone calls and emails in detail, and if by the end of that I still wanted to respond, then do so, it was a clever idea, it reminded me of all the good we do and how much Mary needs us, it also helped to see things a little more from the point of the family, of corse it doesn't change the fact that Dave is a bully, but sometimes it helps to look at the overall picture.
And your partner should start looking for a new position and a new place to live now. You need to have a plan for the future, because if the relationship with the family breaks down you could find yourselves in a bad situation.
I've been quietly increasing my work load, Julie and I had 30+ clients (housecleans), we give up 60% to move in with Mary, I've also asked a couple of former landlords to keep us posted of available places, but if things do change, we'll probably take a break in India for a month, so this gives a little more flexibility.
I'm not sure if we'd do the live in care work again, at the moment it's easy to say we would, Mary is such a lovely lady, but if Dave's actions bring the whole thing crashing down, I think it will affect Julie (& Mary) badly, and I imagine she'd be reluctant to go through it all again.
However, the house cleaning business brings with it a lot of elderly clients (that's how we met Mary), when we told our clients Julie was about to become a live in carer, she had 2 serious offers to become a live-in carer for clients, one offer was £800, but the man had a serious alcohol problem, so Julie would never consider it, the other was £700 a week (double what she's getting now) for a really lovely man, Julie had helped him a lot when his wife was dying, and he had Parkinsons, it really hurt Julie that she couldn't help him, but she'd already agreed to move in with Mary, and she keeps to her word, he died a few months ago.