The healing boon doesn't say target with a healing power, it says use one. So I'd think it works when you target someone else with the healing power and also use it on them. The immunity to close and area attack is so enemies have to specifically waist an attack to get rid of your spirit. Winking it out is an attack you DIDN'T take. And spirits can 'shift' for 2 of your minor actions sorta. Unsummon then summon anywhere 20 squares or less from you.