This is my response to you:
(1) What is the process to obtain a clear property title now?
Answer: Firstly do a Title Search Report through an advocate. Then let your appointed lawyer examine your title and the claim each owner has;
(2) Do we need probate or succession cert.s and/or Letters of Admin?
Answer: If there is Will. Then probate otherwise succession certificate will be enough;
(3) Do we need NOCs from sisters at each level of each branch?
Answer: If it is ancestral or even self-acquired then you will need NOC from all the legal heirs, Class I or II or III;
(4) Is it true that max charge for the probate is ₹75,000? (5) Any other requirements?
Answer: There is no charge. You will have to pay court fees etc. Consult a local lawyer and then go ahead with the same.