What the board is doing is certainly not best practice, but I doubt that it is illegal.

I am not aware of any law that requires minutes of board meetings, but the organization has no reliable record of what happened if they don’t keep them.  (See Ready Reference Page:  “Preparing Minutes of Board Meetings Is Usually More Art Than Science”)  The Chair can cancel meetings whenever he wishes as long as the rest go along with it. And they don’t have to tell you what they talk about in executive session.

If the organization has a whistleblower policy, threatening you for making good faith complaints about their procedures may be a violation.  But somehow I doubt that they have a whistleblower policy, at least not one that they pay any attention to.

If you aren’t on the board or a voting member and have no right to force the issue, you might try to get the organization to consider adopting the Standards for Excellence for nonprofits that were created by Maryland Nonprofits and are being promulgated by a number of state associations of nonprofits.  Or you could investigate other standards certifications or accreditation procedures.  They would all give outside validation that the current practices are not adequate.  But if that doesn’t work, you probably have to weigh whether you can contribute enough to the mission while working under the rogues to make it worthwhile hanging around.