SQL Server XML Insert Optimize?
Can you stage it twice?  First, shred the data into rows of XML, and then read the columns from the rows.  Something like:

with XmlNamespaces ( 'urn:xpaykj-report-xml-1.0' as xkj) 
    Select  
     xItem.query('.')  as RowXML
Into #loadtemp 
    From @xmldoc.nodes('xkj:output-data/xkj:childs/xkj:child[@name="output"]/xkj:childs/xkj:child[@name="lvla"]/xkj:childs/xkj:child[@name="lvlb"]/xkj:childs/xkj:child[@name="lvlc"]/xkj:properties') as x(xItem) 


should give you rows of XML; then apply your value statements to shred the table into columns.