Epic Cardboard

The motorcycle doesn't actually work as a vehicle. All it is is an equippable motorcycle item that speeds up player movement. It's not a genuine vehicle by any stretch. Obsidian originally wanted to include vehicles in New Vegas, but quickly learned that it is just not possible with the Gamebryo engine.

Weapon sway is affected by four variables: the strength requirement for the weapon, whether you're crouched or not, your guns skill, and the condition of the gun. If you hover over the gun in your pip-boy, it gives the ideal gun skill on the left, and the strength requirement on the right. If you don't meet these, your weapon sway is usually really noticeable. If you meet/surpass them, it's incredibly minimal. A mod isn't needed if you understand how it works.

I don't think it's possible. There's way more variables than you've listed, like NPCs being shared clientside. People were barely able to make Torchlight multiplayer workable, and New Vegas is a much more complex game.

It's not possible with the Gamebryo engine. People have tried many, many times.