Child support remains modifiable, either on periodic review every three years, or on a showing of changed circumstances, at any time during the minority of the child. It is impossible to make it unmodifiable, as the Nevada Supreme Court recently held in the Fernandez case, which is or will be shortly posted on the child support page of our web site, at http://www.willicklawgroup.com/child_support.
As to time share and its effect on child support, the Court has altered that as well -- see the Rivero opinion, already posted on the same page.
You don't supply enough details to determine whether the other matters are really modifiable under your current circumstances, but you should be able to make a preliminary determination after looking at the resources posted at:
If you decide you would like to discuss this with one of the attorneys of this firm, please take a look at our consultation policies, procedures, and costs, at http://www.willicklawgroup.com/consultation_policies.