I am working post divorce issues as per my contract. Contract calls for mediation and or if that fails binding arbitration. Issues of alimony and educational agreements. My exhusband has an attorney I do not. Attorney has advised ex husband to lower alimony payments and not pay educational expenses even though contract calls for renegotiation for these issues. Do I send a request for mediation and or arbitration in the same letter, and how much time should I be reasonably required to wait to get a response from his atty for request to mediate in NC?

There is no rule for what is reasonable in terms of hearing back from opposing counsel. I would say a good rule of thumb though would be 10 business days.