Matching white backgrounds across multiple images

Hi.  I know it is a bit late but i was searching the same question.  In the end I used Photoshop Magic Wand tool to hilite the entire area around my subject which took at max 3 shift/clicks with that tool then filled with a consistent color  i.e. white.  Turned out well.

To help position the eyedropper at the same position in each frame, try the Loupe Overlay feature (View > Loupe Overlay submenu). After you choose View > Loupe Overlay > Show, a grid appears with crosshair guides. To edit it, hold down the Command key (or Ctrl key in Windows), and some settings will temporarily show at the top as long as you keep the key held down. You can change the grid values by dragging the numbers at the top, but for the question we’re talking about here, what you probably want to do is drag the crosshairs and drop them at the position where you want to consistently click the white balance eyedropper. After setting it up, as you go from image to image just click the eyedropper at the crosshairs.

But you need to be careful where you position the eyedropper. There's quite a bit of red reflection near the gloves, and I can imagine this is the biggest variable here. Near one of the corners is best.

You really need some sort of grid to put the eyedropper in exactly the same position. The variance in the background is such that a few pixels off will yield a bigger difference than you already have.

Use the white balance tool. Click on the background with the tool.