Thanks Jerry and everyone else. . . . things have calmed down considerably.
Dad is feeling much better and is out of the hospital. He's more comfortable at home with Mom even tho he now understands that he's going to need a lot more help. One of the two crazy sisters has sort of come to her senses . . . she realizes now that she cannot do everything and has started working with my brother and me to keep things going and get all the new stuff that needs to be done handled.
Dad's realized that I never intended to toss Mom in an old folks home (he's thinking old fashioned not so nice places) as soon as he was gone or toss the crazy sister out on the street, so I've been reinstated as executrix (never was actually removed as the will hasn't been rewritten). He's working with me, a sister and my oldest brother on getting his will updated and plans made for Mom.
Dad's also decided to accept treatment - radio wave therapy and chemo injected directly into the tumor. Chemo handled this way and with the particular mix is not supposed to cause nausea. The treatments won't increase his time, but will make him much more comfortable. The longer he's able to do for himself, the happier he'll be. When Dad's not happy, nobody is happy.
There's a lot to be done, but for the moment all is well. In some ways, things are better than they were before this last crisis.