If my suggestion in #1192 was taken:
Alternatively it might be easier to just create an ad hoc dialog normally at the call site and set it up as needed, to avoid affecting all the callers of dialogs_show_question_full() and friends.
Then the first and fourth items would be trivial to solve compared with trying to adapt the general purpose helper dialog function which is currently in use.
Personally I think it'd be nice to get rid of this modal dialog and find another way to let the user know the search wrapped back to the start. One rather nice example is QtCreator which flashes/fades in/out a "referesh" type of icon, overlaid on the middle of the editor like this:
