Questions about Steamgifts and games removed from Steam (+giveaway)

First non-public giveaway: Battle vs Chess (but Steamgifts lists it as Check vs Mate, which is confusing, so I figured this was better given where people are more likely to read the description). More info in the giveaway.

That aside, I've been wondering how things work for games that can no longer be bought on Steam. The faq and trying to search hasn't helped much. I know Steamgifts checks prices on Steam automatically, and when non-bundled games go down in price so does people's CV for the game.

But what about when the price goes down to zero (either a game goes permanently free, or gets removed from purchase)? I can't imagine people's CV goes to zero for the game because that would be insane.

What about giving a game that's no longer up for sale? (This part isn't just curiosity. I realized I have some stuff which isn't up for sale anymore which I would probably like to give.) The closest thing to an answer I found was in this ended giveaway, where someone said you have to contact support to get any CV for a non-purchasable game. But the giver never got a support response.

Does that mean you should contact support ahead of time before giving a game no longer for sale (if you care about CV)? AFAIK support is perpetually overloaded so I don't like the idea of contacting support unnecessarily. I'm really hoping someone knows the answer to this.