Are the curation rewards Smart Steem earns through these delegations split between those who've delegated?

No, due to the 13 weeks power-down period. That's why we decided to use SmartPoints. Keep in mind that the main goal we had was to provide a useful platform for Steem. Earning Steem via delegations for SmartPoints wasn't our main goal, it's rather a positive side effect.

I fail to see how that positioning would give me equal to or more curation reward compared to if I simply kept my 30000 SP and voted on my own.

There's no guarantee that you will make more curation rewards, compared to voting without SmartPoints. It's also important to note that we can only take care of how fast the votes go out from our end, not how long it takes for the RPC nodes to process them. This can result in a partly randomized order.

However, let's say you delegate 5000 SP for 1 month (+5 days CD), you'd earn 150 SmartPoints, more than the majority of the users.

Last but not least, our goal is to provide more utilities for SmartPoints than just preferred voting. This is simply the first feature we implemented. So please don't judge SmartPoints too quickly, as they haven't nearly reached their final usability.