The Sentinels vs. Spite

PL626 Compound Xi states "Whenever a hero uses a power, Spite deals them 2 toxic damage etc. etc." - so putting the name of that hero into the sentence and replacing "them" with the name again normally makes perfect sense, e.g. "Whenever Legacy uses a power, Spite deals Legacy 2 toxic damage".  But when it becomes "Whenever the Sentinels use a power, Spite deals the Sentinels 2 damage", it becomes a bit of a problem.  The card does NOT explicitly deal the damage to the character card which used the power, so this means you could have Mainstay keep taking the damage even while you use The Idealist's power every turn.  Is this as it's intended to be?  It seems wrong somehow.

Also, to be more esoteric, say that Spite starts with the Lost Child in play, and then Mainstay uses Block on his turn.  When the Sentinels's next turn starts, is Block still in effect when Mainstay chooses to take damage saving the Child?  Does the answer change if the Lost Child enters play after Block is used?

One last question, which I'm sure has been asked and answered before, but I have no idea how you'd search for it...when Spite flips and destroys all Victims not in the Safehouse, does he regain HP for their deaths, then take the damage for those that were safe?  Or does it happen in some other order?

My understanding is that the Sentinels have the powers collectively.  So the damage goes to the hero - The Sentinels collectively - and gets pushed onto whichever target you choose.

Yep, same as Infection - one hero is Infected, but as the Sentinels are collectively one hero, you then choose which of the four individuals recieves the actual Infection. Same goes for anything else which targets the Sentinels as a "hero".

On Spite flipping - the condition for him hitting himself for Victim damage is that he has flipped - once he's flipped, he no longer lifetaps, and the Safehouse specifically triggers on his "flipped to Drug-Wracked Monstrosity side". So he'll then hit himself for "Victims x 5" damage and soak H-2 points of the damage (from that drug that lets him soak once per turn) but also deal +1 damage to himself (from the damage-buffing drug). If H=3 then the two cancel each other out.

That is correct, the sentinels are using a power that is on one of their cards.  not that you can't play it other ways.  

I believe Lost Child says at start of turn, while block only lasts until the start of turn, so block would fade before any start of turn effects trigger.

This is not really what I asked.  Say he has 8 of his 9 Victims in the Safehouse and is at exactly 40 HP when he flips (and it's not Advanced), and we'll let (H)=3 so that the bonus and penalty will cancel as you said.  So when Spite flips, he's about to take 40 damage and kill him…but first, he destroys all Villain cards in play except Drugs, so if he has the ninth Victim out, he's instructed to gain (H) HP from the Victim's death.  This has nothing to do with the lifetapping.  So does that happen before or after he takes the Safe House damage?  For that matter, what about his advanced version healing?  It's extremely likely that Spite is at full HP when he flips, so does he waste all his healing first and then take the safe house damage (because the instructions happen in card play order - first his character card, then the Safe House, and then any destroyed Victims)?  Or does it happen in some other order (perhaps first destroying all Victims and resolving the HP gain from them before moving on to the Advanced healing and then the Safe House damage, or perhaps the Safe House damage should come first since that instruction was in play even before Spite flipped, and triggers before the actual text of his B-side "loads"?).

Do them in the order that you think best, it's a rule15/Order of Operations thing, it's not happening because it's the start of the turn, that was just the instruction to flip him.

But saying that flipping a card changes when they entered play is jibber jabber. Do Omintron's ongoing trigger before he flips because they were in play before the flipped side? What about the Matriarch's birds? Or Voss' minions?

The character/rules card only enters play once, at the start of the game.

That's not precisely what I meant.  I know that it doesn't change the order of the cards entering play; my thought was that a previously-in-play "when the villain character card flips" effect might conceivably happen the very instant that the flip occurs, before any text from the newly-flipped side can be applied.  Imagine that the Safe house goes "ding" as soon as the card is perpendicular to the table, whereas the text doesn't appear until it lies flat on the new side.  May not be how it works, but I thought it seemed logical.  It would not apply to any other triggers except maybe Blade and Skinweaver gaining HP when they flip for hitting 0; I don't think there's another card which isn't the villain character card but has effects that happen when that card flips.