Wearing the Patronus isn't any more dubious than casting it inside of Hermione to revive her. You're right about stunners instead of AKs of course, but that can be blocked by a thin invisible tranfigured shield (air into glass, since apparently he can transfigure arbitrary atomic structures). Transfiguration is wordless and he has a wand. I mean, this isn't anywhere near as deus-ex-machina as half of the Azkaban escape anyway.