Heather, When you get some of the things narrowed down and he's agreeable, suggest getting a life insurance policy that will indicate that his daughter(s) are the beneficiaries. He may not think it's necessary, but it's a good one to have in place because of your youngest daughter's condition.
KML, It may not be legal the way I suggested, but there are many that do it and come out the other side when their spouses are killed. I know of one case whereby my xh's step mother had a policy drawn up on his father after they separated and he was living w/ow at the time of his death. She never let on she had the policy until after the funeral and she came away w/a nice chunk of change. I don't know how she pulled it off, but I was always "shocked" by what she did.
Heather, I think you are on the right track.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.