Curating

Depending on the amount of STEEM Power you have, you do not want to upvote a post before it is at least 30 minutes old. (This rule may change to 15 minutes with the next STEEM blockchain hard fork.)
The rewards you see on a post is split 75/25 between the author and curators.
Curation also depends on your voting power. I do not generally let it fall below 90%.
You can monitor that from the following tool:
https://www.steemworld.org/@sorin.cristescu

Curators of a post share in the curation reward (25% of the payout) based on voting power and STEEM Power at the time of the upvote.
Down votes do not earn anything for the curator.

Down Voting Flag

You are correct. The flag is for down voting.

I have seen flagging (or down voting) used when a person uses inappropriate tags on their post. For example, an author sees that posts using the #photography tag get high payouts on average. So the author uses the #photography tag on a post that has nothing to do with photography. Flagging the post and letting the author know that use of the photography tag was not correct for the post is an appropriate use of down voting. Please note, this was only an example.

I have a bit of voting power to spare right now, so I will take a look at your blog.

Steem on,
Mike