Regarding your first question, yung anak and the surviving spouse muna ang mas may better right kesa sa kapatid ng namatay. So bale ganito yun, half ng properties ng deceased sa surviving spouse, tapos the other half sa mga anak including the share pa ng surviving spouse.
Second question- You are right, hndi legal ang divorce dito sa Pilipinas. Pero if in your case yung babae nangibang bansa, at naging American citizen, pwede siyang mag-obtain ng divorce sa ibang bansa para mapawalang bisa yung previous marriage. However, since foreign judgments are not recognized in this country, kailangan pa niyang mag file ng petition for the recognition of judgment of divorce. Note that this applies only kapag naging American citizen na siya. Any divorce obtained by a Filipino abroad is invalid.
maraming salamat po sa sagot nyo, naliwanagan na ako. ^_^