buyer of co-op unit refuses to sign Acris

[Wendy Rosmarin]

Want to sell unit in small multi unit coop. According to bylaws, buyer has right of first refusal since is insider and owns majority of units. There are many other restrictions in bylaws as to whom we can sell.  Promised to buy but at last minute refuses to sign acris.  We want to pay taxes on sale but need his signature on form. We are being held captive by his refusal to do what is legally correct. He has tried to do other illegal things and manages the coop as well for years. Received financial accounting yearly statement only once and do not have meetings which are in bylaws. Suggested by lawyer we sue. Any suggestions to avoid paying thousands in legal fees?  Do we have to continue paying maintenance to him for empty office? Can we change the bylaws?