expanding “fair use”

I’m not talking about fair use, I’m talking about public domain; complete freedom to modify or redistribute.

Said pain should be rewarded

Yes, by temporary monopoly

Amazon shouldn’t be able to find something just outside of the copyright window to copy and redistribute.

Why not? Project Gutenberg provides an incredible service (and LibriVox) which is based entirely on the concept of old works naturally falling into public domain. Imagine how absurd it would be if you still had to pay the publisher of Charles Dickens to read A Christmas Carol.

some content farm could just copy a video, reupload it, then rake in all the profits

Do you see content farms making bank with public domain content now? This is a ridiculous scenario, you obviously have not thought out this issue and instead are just justifying your feelings on the matter. Old things belong to everybody, culture is meant to be shared.

because copyright for small creators is rarely enforced

That’s a completely separate matter bud, go ahead and advocate for enforcing the law for small creators, I’m talking about what the limit for those protections should be.