Legal Question in Family Law in North Carolina

You need to speak to a family law attorney. Typically, one cannot "sue" for more alimony at a later time. You need to get advice as to what she can and cannot ask for.

Your questions don't make a whole lot of sense without additional information. How could your ex-wife use money/financial assistance provided to your children against you? Why would you assume your ex-wife would or even could sue you for additional money - especially 'alimony' and especially on the basis that you son has now reached the age of majority? So what! Further, unless you specifically agreed to it in a Separation Agreement or some other document (not at all a wise thing to do) - child support ends at 18. There is no obligation to pay or support a child through college unless you want to and if so, that money would most likely be considered a gift to the child.