@Anarki: No, since that is a Protect spell, it can only be used to protect. You can not change the Intent of a spell by using it for something else any more than you can use an earth spell to do fire.
Regarding the duration: That is the duration of the actual magic. People killed by a harm spell will, of course, stay dead. That doesn't mean the duration is "forever".
Same with creations. You can create something out of thin air and it'll remain when the magic is over, but it will be subject to normal wear and tear or it could just fall over.
