Legal heir and property after mother�s death

Hello our mother died recently living behind her immovable property without any will. She has a son and a daughter. Our father, 80 years old now, separated for another wife 40 years ago and never lived with our mother. He lives in the same city but at a different house and owns a lot of properties himself (which he always wrote to his second wife name). He also has a daughter from that relation. But they are not legally married. My brother and I are trying to figure out how to transfer my mother's property to our names without involving any civil law suits or long case. My mother never got divorced or took any legal action against him. There is no will. We have gotten the death cert and legal heir, which states all three names. We could not avoid his name as he is still the legal husband of our late mom. In addition, recently our father managed to get hold of the original documents from one of the old lawyers office which my mother had used but didn�t collect papers before her death. Now these papers are with him and he is demanding a lump sum money to return the papers to us. He says doesn�t want any share of the property but at the same time he is not showing any interest in working with us to transfer. The property was completely purchased and held by our mother all alone. 1. What actions can he take with these original property papers? 2. Does he have more rights in the property than the children? 3. We have occupied the property ever since mom�s passing and we are operating it currently. Can he gets us evicted? 4. Can we obtain copies of the property papers in original somehow? 5.Can our father take mortgage on the property using the original papers? 6. What should we do to keep operating the property and eventually transfer to our names? 7. After his passing is there a danger of his second family fighting us for ownership or share of his portion in this property? Like his daughter asking for 1/3 of his share? Thank you!