Okay, the Elfa shelf is in place.
http://i.imgur.com/9eyUTwF.jpg
Used a total of 1 molly screw and a wood screw, reused the remaining except for the one in the middle.
http://i.imgur.com/bJQEpZD.jpg
We first tried without the white shelf, which is why you can glimpse white pads on the brackets. However, we weren't completely satisfied with the appearance, so we're trying it with the shelf for a while (it'll probably adjust itself after a year or so).
http://i.imgur.com/iugrjld.jpg
Let the middle plug stay a little longer, you never know if you might change something back

So far it feels good, much more stable than before.