To my mind, it could not work from the external jsSoap.js because through soaprouter.jsp you can accede only to schemas defined, with WSDL definition. And temp:enrich_broadlog doesn't have such a WSDL definition.
So I suggest you to:
extend the target dimension factory schema (I guess it is nms:delivery?) with some elements or attributes, for instance cus:delivery.wfkStatut
in the workflow, use save entity method to store the status value in wkfStatut element or attribute after your JS activity jsWkf
so within the jsSoap.js thanks to the WSDL knows this element/attribute and gets the value.
Alternative way: instead of extending a factory schema, create a custom schema if it is more convenient for you.
As several posts related to workflow query/enrichment activities mentioned, you can't accede directly to your xml context but must run a queryDef, because query/enrichment elements (targetData) are only made for delivery activity or standard activity access, and not accessible directly from the context (it is different from webApp).