I'll spare the details of long emails and voice mails that they have sent threatening us with all sort of legal action, etc. if we do anything to work on the unit that disturbs their well-being, or do anything that seems retaliatory.

A week passes no check, tenant stalls some more, my son threatens to file with Landlord tenant board.

They feel threatened because they are facing the real probability of being homeless.  

A few months ago they had a bad tenant and her boyfriend started verbally threatening them over a security deposit deduction.

Don't let her threaten you, you are the one who can enforced any rules at your property. 

Saying C is inherently irresponsible, and threatens the viability of a real estate investment because he has no cash - is not your best approach either.

Personally I hate the attitude many have of serving eviction paperwork immediately on people or sending threatening documents.

I don't see the need to threaten me with eviction.He is very shady and I planned on him trying to keep my deposit, but this is just ridiculous.Am I legally bound to this 30 day notice if my termination was a result of his untimely and possibly illegal rent increase?

They said they threatened to shut off the power but never actually did it.

First I would try to threaten the sellers with legal action, if that did not work go to small claims court.