1.: I would clearly support a convergent linear reward curve!

2.: I could live with higher curation rewards, even if I don't support it:
It's hard enough for new users anyway: to create an account, have enough RC for upvoting and answering comments, earning any small amount with their posts. It would get even worse! And if then for example I would be one of the few upvoters of such a small new account I would get a big part of the reward myself (as curation) instead to be able to give it to the author ...

I really like to curate already NOW with only 25 % curation reward if I find good stuff (I don't care when I vote and who else did vote). I curate because I like what I see. I think the voting behavior of people who are curating this way wouldn't change much with higher curation reward. I guess only people who curate just for earning money, most of the time in an automated way (without reading what they curate) would be affected by this change. And they still wouldn't support new users anyway. Thus they still wouldn't support the growth of the platform.
To my mind, this kind of voting behaviour, which is geared towards short-term profit, only apparently leads to a higher return on investment: although more STEEM is acquired, the STEEM price is reduced by lowering the attractiveness of the network for the majority of users and thus also potential investors. I would like to forego earning even one more STEEM if I knew that this would raise the STEEM price to 20 euros in the long run ... :-)

3.: As I have already stated in My STEEM Vision. (I would appreaciate you to read the full post), in my opinion the suggestion to provide each user with a certain number of 'free downvotes' (by adding a "downvote pool") so that spam (or overvalued posts) would be flagged more frequently in the future, wouldn't really make a big difference under the current conditions. I assume that only whales flagged more often than before, while smaller accounts would still not dare to do so for fear of retaliation.
As I have described in my post, I think flaggs (downvotes) are an important part of the STEEM ecosystem, but at the same time users should be protected against 'despotic' flagging.