Free: Contests & Raffles.
If it were a really good deal then why not. If just an average deal I don't see the need if you already own a .280. If you want a step up to .284 from the .280 I would go with a 7mm RM.
Absolutely no need for a 284 if you have a 280. Especially with you not being a handloader, the 284 ammo would be unnecessarily expensive. I'm sure you have other things to spend your money on.
No, you should not. You should buy ammo for the end of the world
The reason there are so many Ruger upgrades is because they're necessary.