The court may modify any provision of a deed, agreement, or settlement with respect to the care, custody, education, or support of any minor child of the spouses, if the modification would be in the best interests of the child. The court may modify any provision of a deed, agreement, or settlement with respect to spousal support executed on or after January 1, 1976, regardless of how the provision is stated, unless there is a provision that specifically states that the provisions with respect to spousal support are not subject to any court modification. The court may modify any provision of a deed, agreement, or settlement with respect to alimony or spousal support executed on or after April 13, 1976, regardless of how the provision is stated, unless there is: an express waiver of alimony or spousal support; or a provision that specifically states that the provisions with respect to alimony or spousal support are not subject to any court modification.