A good starting point for an answer would be the help and tour pages - you can find these on the top of the page. Read these.
You can't @ someone who hasn't replied to a post - a correct use of an @ would be when talking to multiple people on a comment thread.
As for getting your question on the front page - SU has a reasonable amount of volume and a lot of experienced users tend to use other means to find questions.
Should you have sufficient rep you could offer a bounty (but I wouldn't recommend it here). Otherwise the only thing to really do is to wait for an answer.
In addition, David Postill isn't a moderator. He's just a particularly active and helpful user. Once again, have a look at the help to see how the site works