[2020] PvP newbie - some questions

1: Pistol does decent damage, but, it really depends on where you hit them and what kind of armor they're wearing, and what perks they have. A fortitude built person in full steel armor won't even notice the pitiful damage of a pistol; especially if it's body shots and not headshots. Headshots vs Bodyshots matters heavily as well- And whether or not you hit the uncovered face/neck or the actual helmet will determine if it gets reduced damage or not.

So in essence, Yes, It's very possible depending on what the other guy had for him to just blow off 7 pistol shots. He may even have used a healing item like painkillers or fort bites to buff himself up.

Edit: Also important is the quality of your pistol and the mods it has on it- A quality level 1 pistol with no mods won't do much damage to even an unarmored player without headshots.

2: Landclaim affects all blocks within it's radius from bedrock to sky- Including terrain, at least so far as I know. I've never had much leave to test it as I only ever play co-op with my sister.

3: Almost certainly. Who would build where someone else can easily locate and steal in a PVP server? There's probably a fair few that even don't use landclaims as it's a bit of a giveaway.