OCI when divorced but have Indian Parent

Hi,

I'm British by birth. My dad kept his Indian citizenship but mum (Indian by birth) took UK citizenship. Both have passed away. I was married to an Indian citizen but divorced 16 years ago. I did not remarry etc.
(1) Do I need to give 'spouse details' when I don't have a spouse? I heard he lives in Australia now - we have no contact whatsoever.
(2) I know his old Indian passport number from when we married - do I provide that or leave blank?
(3) I wish to apply on basis of my father being Indian - is it enough proof of Indian origin if I only give copy of his passport?
(4) What other docs do I need? I know I need to provide my birth certificate with parents' names.
(5) I don't have my mother's British or original Indian passport - will that be a problem?

I hope someone can advise