Raws and translations say Wei Wucai so I am sure that is his name. As for the Gui/Wei, so far there are no more mentions of the Gui family except in the translation of Two Faced Husband so I like to believe that the Gui was meant to be Wei. But I cannot speak/read Chinese so its either a mistranslation, or a mistake on the author's end.
But I believe the Gui is Wei. Lol.