I really feel for you - we had a similar situation and , I am ashamed to say , let it go on far too long.
MIL was the one attacking FIL , and me - sometimes with a knife but she was 'sweetness and light' when any visiting professionals were at the house. You have evidence on the camera, I would suggest that you ask the UCR worker to put in writing that they felt threatened as well.
It took us a long time to realise that trying to keep them together was the worse thing for both of them and we needed to look at them as individuals , each with their own needs.
FIL went into care and had the time of his life for the 18 months he was there before he died.
MIL was not happy at home on her own, she should have been in care but had 'fluctuating capacity' - the biggest cop out ever for social services!!! - eventually she was sectioned and has now been in a different care home for 2 years and is more settled, and better fed, medicated, dressed and clean, than she was at home.
Hope you manage to get sorted out.