All politicians meet with lobbyists. It’s hard to get a handle on the needs of the nation (or state, or so on), and lobbying is how people inform their representatives of that need. Now whether those lobbyists are scumbags or saints, that’s a different question.

The latter. The US only has a veto in the Security Council. Though even that isn’t entirely unconditional. Recently it abstained on a vote about a cease fire resolution, leading to much entitled complaining from Israel.

Don’t worry, they’ll pass another strongly worded resolution.