Does my father's widow have all rights to property my father acquired before his marriage to her?

Your question would be governed by NY law.  I can tell you that generally, your father's wife would not have all rights to the property that your father acquired before his marriage to her.  Under CA law, which is a community property state, your father's wife would be entitled to half of that property under the rules of intestate succession, because he died without a Will.  Under New York law, I found a provision that states, that the property not disposed of by a Will, where the person has a spouse and issue (issue means children) then $50,000 and  1/2 of  the  residue  goes to  the  spouse,  and  the  balance  thereof  to  the  issue by representation.  This means that under New York law, your father's wife would get half of his assets plus $50,000.00 and you and any siblings would take the other half.  You should seek an attorney in NY on the matter probably as soon as possible.