Hello! So the first question would be a similar answer to the question above yours, particularly options two and three. Yes, abilities are nerfed. Jesse can come into the game with Polaris as a presence in her mind (that she is aware of and can communicate with), but we would ask that it's not a helpful presence/beneficial presence. You may also choose to completely omit Polaris instead upon Jesse's entry to the game.

Jesse can bring the Service Weapon in with her, yes. It would definitely be nerfed. It can definitely remain as a gun, but would not have its full uses. I don't see anything about ammunition for it on the wikia — so bearing that in mind, she'd be fine to have it in game in the Grip setting with unlimited ammunition.