OP - I'm so sorry you're going through this. It definitely isn't talked about enough, and it is heartbreaking. My mom passed away a couple of months ago, and she went through an incredibly aggressive, paranoid from November - January. Like your situation, it seemed to come out of nowhere, and it didn't happen every single day. When it happened, though, it got increasingly more violent - screaming, then throwing things, then clawing (she drew blood from me several times).
I know there isn't a magic formula, but here are the only things I found that helped.
- We ended up increasing her seroquel and adding a couple of other things (like haldol). After that, she stopped the violence entirely, she came back off the higher doses, and she was back to "normal" dementia until she died.
- I had two or three "safe people" that she trusted and still recognized. I would call them when she was in a fit and it seemed to calm her down. They would just lie ("the police are on their way to rescue you"), but it helped.
- I was told by hospice staff to repeat "you're safe" to her over and over and to start every new conversation with "you're safe."