The problem with giving it to curators on other posts is which other posts?

Essentially every new post would be eligible, subject to its own reverse auction. Same as now, only more curation rewards.

If you split it up equally according to post payout, then it will mostly just go back to the biggest posts where its lost. If you only give it to posts with little money lost to the reverse auctions (that is to say, don't give it to the sure winners), then youll give a guaranteed payday to anyone voting on a non-voted (or low voted) post after 30 minutes.

Well, roughly speaking, your last point is exactly the magic of it. It's designed to make good strategies self-defeating. If any of this ever creates a guaranteed payday, then people will start competing for that payday in the reverse auction and the payday will vanish. Just like the reverse auction currently takes away curation rewards from sure winners.

You're right, the exact details would have to be thought out well to make sure the redistribution works correctly. But notice that even the "vote every un-voted post after 30 minutes" strategy is essentially self-defeating, because if everybody did that on every post, their votes would all cancel out.