I think the DM's guide solves the "minion hp" question explicitly when it states:
"A minion is destroyed when it takes any amount of damage. Damage from an attack or from a source that doesn’t require an attack roll (such as the paladin’s divine challenge or the fighter’s cleave) destroys a...
Is there any restriction against minions receiving temporary hit points? It seems to me that if a healing effect is used on a minion, they still max out at 1/1 hp. On the other hand, if they're receiving temporary hit points, that seems to throw the entire XP allocation system out of whack...
My method is 1) at the beginning of battle, you get a description. Often, if there are 10^23 creatures that look the same, and one that does not, odds are that the numerous ones are minions. 2) Players may make knowledge checks, and so long as they get the monster name/role then I tell them...