Your questions cannot be answered on the basis of the information you supply, although I can refer you to some resources, and would encourage you to consult with counsel.
Courts may, but are not required, to modify guideline support, under NRS 125B.080, for "the support of others." So having two kids to support indicates that each obligation might be lowered. The relevant charts, guidelines, and statutes and other information on the Nevada law governing child support is set out on the Child Support page of our firm website, at http://www.willicklawgroup.com/child_support.
Given that you are asking about modifications of the custody and visitation schedule for the other child, you should also look at the very large amount of information posted on the Child Custody page of our firm website, at http://www.willicklawgroup.com/child_custody_visitation.
You should probably seek consultation with an appropriate family law specialist. I would suggest starting your search with the American Academy of Matrimonial Lawyers, the Nevada chapter of which can be viewed at http://www.aaml.org/go/fellows/fellows-by-state/?showResults=true&state=NV. Good luck.
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.