As a US company they are required to get launch permits from the US regardless of where they launch from. Mixing jurisdictions would likely make things harder, not easier.

The FAA has control over them no matter where they are. They cannot escape.

Probably nothing, but that would surely be quite the feat. Just getting the necessary people there would be difficult, let alone the supply chain and the structures. Even operations like SpaceX need some degree of efficiency.

This launch is intended to test the ability to land on the original launching tower, which is a core ability to the intended economics of starship; launching offshore would defeat much of the purpose of the launch.

Itar