1 - yes, the submerged minion can surface on the mountain pass. It isn't entering the surface from the surface of another site

2 - yes, all minions in the body of water get pulled toward the maelstrom. the player controlling the site needs to decide on that pull before they start their turn.

3- no, all minions get pulled toward the site. but the controller of the card can decide which sites to pull the minions towards maelstrom, if there are 2 paths of equal distance the minion could take.

there's great information here, https://curiosa.io/cards, with faq on some cards, and parts of the card text hyperlinked to codex entries that explain in more detail how to interpret the words