If the 10 weeks of summer were included in the same agreement as the $1500 per month, a judge looking at this now is going to assume that the dollar amount was arrived at with the summer weeks already taken into consideration, whether that is historically true or not.

The child support has to be paid, as it is, until and unless a court orders otherwise.  It is a very bad idea to stop payments on your own, for any reason, unless you file a motion with the court to end your support obligation, for a very good reason, at the same time.