Proposed Society Creation & Non-cooperation of builder

Hi, We bought a house from relatively a known builder in mumbai 3 years ago. out of 42 flats, only 17 are occupied and rest are ULC reserved flats. Till now, builder has not done any maintenance related work...we dont have bMC water connection, building is not painted yet. During last meeting he told us he will work on 10 pending items and for that we need to first clear our maintenance amount. Post clearing, he is now directly saying i will not do anywork and take whatever action you want against me. Now my queries: 1- can we form a proposed society with 40% occupancy? If yes, then what is the expected cost of creating a proposed society? once a proposed society is created, do we have legal rights to do builder development activities like painiting, etc? 2- can we take legal action against such a big builder? will be worth or it would be just waste of time and money? 3- what can we do inorder to force the builder to register the society since now he is charging 5 lakhs from us incase we wish to sell our flats? Thanks in advance