It's fair been on my mind, your message, as for me it is a dread situation.
I hope it works for you, of course. From what you say it seems like there is some substancial shift to be given consideration, and as Colombo says, 'When a snowball begins to move, you push'.
But, when I think of the hell and trauma. I think that if I was put in your position I would insist on the therapy, as you have, but I would say that I would only accept the exchange of birthday and Christmas and mothers' day cards, and perhaps later letters. And I would state plainly that any attempt to develop this into face-to-face or mouth-to-ear, or any kind of subtle manipulation within the cards or letters, would be seen as manipulative control and would cause this last chance to cease for ever.
Anyway, all the best with it, and remember to think of taking care of yourself, as you are only human and have your limits of what you can cope with.
'.................Oh, er,....... I was just wondering if, er, Marm, I could just..... one thing I forgot to ask..............'