I would think something using GetValue and/or GetAsNumber and some form of Evaluate( Substitute( text; ¶; "+" ) ) might be worth a look.
Maybe run what you have with slight change to hold the "," in there and then add "," to the filter and then use Evaluate( Substitute( text; ","; "+" ) ).
create a list from those text fields (replacing ',' by a FileMaker Return character), filter elements as in Your example -> and use a custom function for adding the values.
www briandunning com, ie SUMLIST(list) by Martin Spanjaard
"Can you help me with a function to sum up the total numerical values in a textbox separated by ,"
Evaluate ( "Abs ( \"" & Substitute ( YourTextField ; ", " ; "\" ) + Abs ( \"" ) & "\" )" )