The 4 posts/day is true, and it's calculated probably on UTC time, the same day in UTC time, so if you've posted the 4th post at 23:59, you can post again 4 after 00:01 becaue it's another day. It's based on days, not 24 hour period. So the http://www.steemdollar.com/limitstatus.php is a little bit wrong, maybe @mauricemikkers can fix it.

It is good to vote before others, but if somebody with bigger SP votes after you, he might get more curator reward than you. Also if you have few SP, you wont earn alot from curation, you need to get more SP.