Fore/background - no unfortunately not. The line is drawn on the chart "overlay" - a transparent panel over the chart. The reason for this is that the chart has to be allowed to change under the line. For efficiency's sake, MT's charts do not redraw the whole chart unless a new candle is drawn. When the current candle is updated, only the small vertical slice of the chart on the right containing the candle is redrawn.
With indicators and regular paintbars that is no problem since whatever changes is also in that vertical slice and gets redrawn. But the SetLine lines may change over the whole chart, there is no restriction for that, so they cannot be drawn on the chart itself. They are instead drawn on the transparent overlay.
This efficient drawing algorithm allows MT to handle massive number of simultaneous charts without overloading the computer.
As for Shares Outstanding - try I think the shares outstanding is just a number.