I don't know of any state where the laws of intestate succession give everything to the mother if the father is still alive.  So I'm not surprised that she doesn't want to share any documents.  When you say she keeps the title to the car, do you mean she has the piece of paper that says it is titled to the corporation?  The corporation should be able to get a duplicate title.  The funeral expenses take priority over distributions to heirs, so it looks like time to consult a lawyer.