Is there a tool or other way to estimate...

Don't think so

I remember reading AP/Box was around 300 for both Nerofest and Christmas assuming you were farming the most efficient node. That should let you calculate the number of boxes.

With an average of 105 stockings per run on the 40 ap stockings quest, it'll take 304 ap, on average, to complete each box (7.6 runs). You can do the math to figure out how much your apples will get you