1) Paralyze is great. It paralyzes common enemies like bandits, but also undead, animals and. Of this I'm certain. If I recall correctly it works even on dragon priests. The only thing it doesn't work on are atronachs and dragons (both tested).
Buy the stability perk in the alteration tree for an even greater duration (+50%)!
2) Grand healing heals EVERYONE around you, including you. So you'll not only heal yourself and your friends, but also your enemies :s. At least on my game, and I'm on pc. I use dual casted close wounds (adept) instead.
3) No it's not. Guardian circle is a cast-and-stay kind of spell. If you can pull off a cast, the circle stays until it vanishes. For best results, cast when etereal.