We had called it a split a short time ago. I live in New Jersey. He has actually called me and said that if I don't give the ring back he will call Dyfs on me for something that happened back in 08. I assumed this was a gift... am I wrong? He said he wants it back but do I have any legal obligation to give it back? I think in New Jersey it's conditional where as if the marriage is not upheld then the ring must be given back

You aren't under any obligation to give the ring back. Some do because what is the sense in keeping an engagement ring if it doesn't mean anything anymore, and probably just in good faith.

Actually in the US this goes by state law.
I'm not going to look up NJ, because you didn't ask this under Law, and you should give it back.
According to the legal site nolo.com, the majority of courts find that the gift of an engagement ring contains an implied condition of marriage; acceptance of the proposal is not the underlying "deal." Absent some other understanding -- say, that the ring is merely a memento of a great trip -- most courts look at engagement rings as conditional gifts given in contemplation of marriage.
There are exceptions (Montana is one) but again - you should give it back. In my opinion