Regarding unfinished building

Hi friends,
Need your help on further execution and understanding…..

I purchased a flat in an under construction building in 2012.

Possession date was 31st Dec 2015.

Building is 95% complete, but open land tax of around 70lakhs is not paid. We are aware that in yearly municipal Corp scheme the tax gets some waiver that time we plan to lower it and pay. But till date this year KDMC (municipal Corp) hasn’t come up with such scheme yet.

Total 18 members in the building, out of which 2 are landlords and 14 ppl have paid full money. Me & my colleague has paid all the due amounts to builder as and when he demanded. Remaining 10% balance amount is to be paid after possession….. Also we both are having home loan too.

Builder has stopped replying, just gives false assurance everytime.

Now All members have come forward to take this project ahead by forming co-op society and bear equal expenses for all remaining work. But the problem is that I have doubt what will happen to my remaining 10% which I haven’t paid to builder. As per agreement i am liable to get 32 lakhs compensation for delay against 4lakh amount i.e. 10% as per the clause mentioned in agreement. So net i have to pay zero.

While forming such co-op. society, what all cautions i will have to take care of, so that society and members dont ask me to pay remaining 10%?

Also whether forming society directly is legal without builders written consent? They have formed the society (which we both are not a part of yet) after giving intimations to builder they say.

Can they go ahead and pay open land tax on their own and complete remaining work of building by appointing other contractor?

Who will give possession to us in this case?

Please help