I want to better understand XSLT 1.0 nested grouping using Muenchian grouping

I have XML data and would like to group it by INSPTR and ELVINSP_DT. Questions at the end of the post.

Here is my XML:

<AS400_ELVPINS00Collection>
  <ObjList>
    <AS400_ELVPINS00>
      <ID>123456</ID>
      <ELVINSP_DT>2014-05-01</ELVINSP_DT>
      <DetailData>Out Sick</DetailData>
      <INSPTR>
        <ID>555123</ID>
        <INSPTR_NAME>Doe, John P</INSPTR_NAME>
        <MoreDetailData>Northeast Region</MoreDetailData>
      </INSPTR>
    </AS400_ELVPINS00>
    <AS400_ELVPINS00>
      <ID>123459</ID>
      <ELVINSP_DT>2014-05-02</ELVINSP_DT>
      <DetailData>Nobody showed up</DetailData>
      <INSPTR>
        <ID>555123</ID>
        <INSPTR_NAME>Doe, John P</INSPTR_NAME>
        <MoreDetailData>Northeast Region</MoreDetailData>
      </INSPTR>
    </AS400_ELVPINS00>
    <AS400_ELVPINS00>
      <ID>123463</ID>
      <ELVINSP_DT>2014-05-01</ELVINSP_DT>
      <DetailData>Job Location was clear</DetailData>
      <INSPTR>
        <ID>555124</ID>
        <INSPTR_NAME>Smith, John T</INSPTR_NAME>
        <MoreDetailData>South Central Region</MoreDetailData>
      </INSPTR>
    </AS400_ELVPINS00>
  </ObjList>
</AS400_ELVPINS00Collection>

I'd like the data listed like this:

Doe, John P  
 2014-05-01 - Out Sick  
 2014-05-02 - Nobody showed up  
Smith, John T  
 2014-05-01 - Job Location was clear  

Here is what I'm trying for XSLT:

  <xsl:key name="keyInsptr" match="ObjList/AS400_ELVPINS00" use="INSPTR" />
  <xsl:key name="keyDate" match="ObjList/AS400_ELVPINS00" use="ELVINSP_DT" />

    <fo:flow flow-name="xsl-region-body">
      <xsl:for-each select="ObjList/AS400_ELVPINS00[generate-id(.)=generate-id(key('keyInsptr',INSPTR)[1])]">
        <xsl:sort select="INSPTR/INSPTR_NAME"/>

        <!-- This part works --> 
        <fo:block>
          <xsl:value-of select="INSPTR/INSPTR_NAME" />
        </fo:block>

        <!-- This part DOES NOT work -->
        <xsl:variable name="vrInsptID">
          <xsl:value-of select="INSPTR/INSPTR_NAME"/>
        </xsl:variable>
        <xsl:variable name="lstInsp" select="ObjList/AS400_ELVPINS00[INSPTR/INSPTR_NAME=vrInsptrID]" />
        <xsl:for-each select="lstInsp[generate-id(.)=generate-id(key('keyDate',ELVINSP_DT)[1])]">
          <fo:block>
            <xsl:text> - </xsl:text>
            <xsl:call-template name="dateFormat">
              <xsl:with-param name="value" select="lstInsp/ELVINSP_DT" />
            </xsl:call-template>
          </fo:block>
        </xsl:for-each>


      </xsl:for-each>
    </fo:flow>

I understand that generate-id creates a unique 'id' at runtime for an element, so I am assuming that generate-id(.) will generate an id for each ObjList/AS400_ELVPINS00 element to use in the match, correct?

What is generate-id(key('keyInsptr',INSPTR)[1]) doing? What kind of results does that make? I'm trying to visualize this.

When I do the 'for-each' on keyInsptr, what Node-set am I working with inside that for-each?

How do I get the inner 'for-each' to cycle through the dates correctly?

I am not just looking to get this working, but to also understand how it should work. Thank you.