Others may have different opinions, but my advice is to retain your own lawyer asap. The situation you describe, a board officer who is uncooperative and a hoarder, a board that refuses to acknowledge or address the situation, multiple ineffective exterminations, apparent gross violations of the warranty of habitability... this will not have a good ending. Your own lawyer will, at least, help you prepare for what is sure to become a litigious situation.

There are probably less expensive intermediate steps you can take such as lodging complaints with 311, the Board of Health, Dept of Buildings, etc, but something like this needs a coordinated, focused approach that an attorney will provide.

If you can't afford to retain an attorney, try searching Google for suggestions. Keep in mind that at some point you and the board will most likely be adversaries. If this happens, having an attorney who is familiar with your situation will save you a lot more financially and emotionally than the up front costs.

Good luck to you.