One simple way, is to back up a bit and instead of reordering a field, just let the Splunk search language do all the totalling for you.
It looks like you're actually getting the 'total' from the data itself, so you'd have to take that out.
If you cant take it out one way or another from the 'main search', you can take it out of your stats output manually with another search clause.
Once it's not in there you can safely use the 'addcoltotals' command (its really a part of 'addtotals' so you can read the docs for 'addtotals')
<main search> | stats sum(value) as mySum by variable | search variable!="Total" | addcoltotals fieldname=mySum label=Total labelfield=mySum
what's that doing is saying -- add up all the columns and put the totals in a new row at the bottom, then in that row, set the value of the 'mySum' field to 'Total'.
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