[SalesForce] Command button and re-render not working

I'm trying to seek some help with the following VF page and the controller behind it, Basically, the outline of this controller is 3 pages…page 1 to capture account info, page 2 to capture multiple contacts for this acct and page 3 to just show the confirmation page….and give users the option to delete the contacts one by one by with a command button.

Now, neither the OnClick action is working, nor is the method getting invoked (I'm unable to see the "inside deleteCont" message in the debug logs) and the re-rerender is not working too…Please advise on what is it I'm missing.

<apex:page controller="newOpportunityController">
    <apex:sectionHeader title="Confirmation" subtitle="Step 3 of 3"/>
    <apex:form >
    <apex:pageMessages />
        <apex:variable var="rowNumber" value="{!0}"/>
        <apex:pageBlock title="Household Information" id="pb1">

            <apex:pageBlockTable id="pbt1" value="{!acct}" var="a" title="Household Information">
            <apex:column value="{!a.name}" />
            <apex:column value="{!a.phone}" />
            <apex:column value="{!a.Email_address__c}" />
            <apex:column headerValue="Action" >
                <apex:commandButton value="Delete" action="{!deleteAcct}"
                                    onclick="return confirm('Are you sure? This will delete Household and all members') " >
                </apex:commandButton>
            </apex:column>    
        </apex:pageBlockTable>

         <apex:pageBlockTable id="pbt2" value="{!contactstoadd}" var="c" title="Member Information">
            <apex:column value="{!c.firstname} {!c.lastname}" headerValue="Name" />
            <apex:column value="{!c.Gender__c}" />
            <apex:column value="{!c.birthdate}" />
            <apex:column value="{!c.Birthstar__c}" />
            <apex:column headerValue="Action" >
                <apex:commandButton value="Delete" action="{!deleteCont}" reRender="pbt2"
                                    onclick="return confirm('Are you sure? This will delete member info') " >

                    <apex:param name="rowIndex" value="{!rowNumber}"/>
                </apex:commandButton>
                <apex:variable var="rowNumber" value="{!rowNumber+1}"/>
            </apex:column> 
        </apex:pageBlockTable>

       </apex:pageBlock>

</apex:form>
</apex:page>

//SPN
public class newOpportunityController {

 public Account acct {get;set;}
 public contact cont {get;set;}
 public List<Contact>contactstoadd{get;set;}
private static final integer maxContacts=5;
public Integer rowIndex {get;set;}
public pagereference page3;

 public static String str1{
    get{
        str1 =  'Are you sure? This will delete Household and all members'; 
        return str1;
    }
  set;
}
 public static String str2{
    get{
        str2 =  'Are you sure? This will delete Member Information'; 
        return str2;
    }
  set;
}
 public static String err1{
     get{
        err1 =  'Cannot insert more than 10 contacts. Please contact the admin';
        return err1;
    }
  set;
}         

 public newOpportunityController() {
  if(acct == null) 
      {acct = new Account();}
  if(cont == null)
      {cont = new Contact();}
   if (contactstoadd == null) 
      {contactstoadd = new list<contact>();}

  }

 public PageReference page1Next() {
  PageReference Page1;
    if (acct != null) {
        Page1 = new pagereference('/apex/page1?id='+acct.id);
        Page1.setRedirect(false);
    }
    else {
        Page1 = new pagereference('/apex/page1');
        page1.setRedirect(true);
    }

    return page1;

   }


 public PageReference page2Next() {
    PageReference Page2 = new pagereference('/apex/page2');
    Page2.setRedirect(false);
    return page2;
  }

public PageReference page3Next() {
    addOneContact();
    Page3 = new pagereference('/apex/page3');
    Page3.setRedirect(false);
    return page3;
 }



 public void addmorecontacts() {
   addOneContact();
   page2Next();

   }

public void addOneContact(){
    if (contactstoadd.size() < maxContacts)
    {
        contactstoadd.add(cont);
        cont = new contact();
    }
    else {

            throw new appHandlerException(err1);
   }
  }


  public pagereference deleteAcct() {
    acct=null;
    contactstoadd=null;
    cont=null;
    return page1Next();
   }

  public pagereference deleteCont() {
   system.debug('inside deleteCont');

   rowIndex =     
   Integer.valueOf(ApexPages.currentPage().getParameters().get('rowIndex'));
    System.debug('row to be deleted ' + rowIndex );
    System.debug('rowm to be deleted '+Contactstoadd[rowIndex]);
    contactstoadd.remove(rowIndex);
   return page3;

   }


  public void saveacct() {
      try
     {
      upsert acct;
      savecont();
      }
      catch (exception e)
      {
           ApexPages.Message myMsg = new ApexPages.Message(ApexPages.severity.ERROR, 'Account insert/update failed:' 
           + e.getMessage());
        ApexPages.addMessage(myMsg);
      }
     }

    public void savecont(){
     for (Contact con: contactstoadd)
       {
           con.accountid = acct.id;
        }
     try
       {
         upsert contactstoadd;
        }
     catch (exception e)
      {
           ApexPages.Message myMsg = new  
  ApexPages.Message(ApexPages.severity.ERROR, 'Contact insert/update failed'
           + e.getMessage());
        ApexPages.addMessage(myMsg);
      }
     }   

     }