I'm sorry to hear what you are going through. It sounds very difficult..

The only thought I had comes from my experience in the care sector.i used to visit patients who were extremely ill and was often unsure as to what to say or do.  I actually found sitting in silence and just being there with them a comforting experience - hopefully for the both of us!

My parents deteriorated very gradually before they died.  When they did die I found I had done most of my grieving before hand a.d their actual death was the less difficult part of the process . It may be that things are at their worst for you now and that things get easier in.the future.

All the very best