I live in Nevada, and my husband lives in CA....We have been separated for 1 1/2 years....can he keep us from being divorced if he refuses to sign?

The short answer is "no."  While the other party ignorning the case can cause some delays (basically, to let the time for answering run, and then take default), divorce is essentially "one party" in the modern world, and you do not need the other side's consent, or cooperation. There could be some jurisdictional issues, depending on which party moved from and to where, and whether there are children, or property, or alimony issues.  See the articles, and information, posted at http://willicklawgroup.com/grounds-and-jurisdiction/.