Your changes seem sensible, but I'd need to know more about the original intent to be sure.
I'd also take a look at what changes the Russian fork has done (Golos?). AFAIK they have two payouts, one after 24 hrs, and one after 30 days, which makes total sense to me as most earning is usually done before 24 hrs anyway, but 7 days is far too short to be able to discover valuable stuff. Ideally I think it should be possible to earn for longer also.
Another thing to consider is built-in language support. If different languages had been properly supported the Russian fork might have been avoided.
Thanks, you've obviously thought about these things. I agree that 30 days is too long default for payout, but that you stop earning money after 7 days is too short in my opinion. Would therefore be interesting to know how it works for Golos. To renew, is an interesting idea, I've thought that perhaps the author could choose length himself, but then he'll also control time for the curation...
BTW: Take a look at @theluke's OpenSteem if you haven't, should be relevant.