1. Doc is a reborn from the Mesa of Madness with a pact to collect souls for the Nameless Sheriff as well as being a phantom rogue. So his recognition of the voice as something familiar ... is not a good thing.
2. In 1e modules, orcs are not particularly friendly; I don' think we have any particular allegiance or requirement within the party to free them. But I am open to reasonable discussion.
3. Don't think so.
We previously made a peace with the stone giants, and are continuing that. We are just trying to end the Hill Giant scourge. Don't make more fights than you need, I guess.
As for why the Hill Giants, it's because they have been raiding and looting, and our mission is to end their baleful influence, with extreme prejudice. If they were to surrender and leave, that would be fine.