Try this :-
DLTSPLF FILE(*SELECT) SELECT(username)
Should delete all the spooled files for “username”.
I am not aware of such a command. The referenced DLTSPLF comes close, but it is not fully outq sensitive (it can handle some specific cases of an outq but not the general case of any outq). It wouldn’t be hard to write such a command though using the List Spooled Files API QUSLSPL. The API provides for selection based on both username and outq. From there you would simply issue DLTSPLFs from the list.
I assume you already used 14 in front of the outq when in WRKOUTQ? 14=Clear