Er.. it is not illegal to sell your channel.
It may be against the Terms of Service, but that doesn't mean something is illegal.
For all we know it is a legal purchase. Like for instance, if the old channel owner changed it to a business name, and then the business was sold to the OP. That is just a change in ownership of the business, even though it is the same entity.
I mean it doesn't look like that is what happened, but, I do want to point out there are ways of doing it legally.
Either way, the question of getting the account terminated is a possibility. When you purchased the channel, was the copyright of the videos included in the purchase?
What I would do is attempt to terminate the contract with the MCN with the fact that the original owner no longer owns the channel or the copyright to the videos(if applicable).
If you own the copyrights to the videos, start moving them over to a new channel, etc.
No matter what anyone says in here, the copyright of a video, is a legally assignable asset. If you have assignment of said copyright, the video is yours do what you will to it.
Either way, start uploading to a new channel... try as hard as you can to convert your current subscribers to the new channel.