- Different white balance is due to your flash tubes fluctuating in white balance; this is common for cheaper flashes. Pro flashes are much more consistent. Just put in a grey card on all your shots, do the white balancing automatic on that in adobe camera raw (og whatever you use), and clone the grey card out of the image once you've used it.
(Note: if you shoot in JPG, you need to lock your white balance to 5500K in your camera)

- Perfect white background requires post processing here. It should take around 1-2 minutes for each image with Photoshop. Using Photoshop CC, simply:
1) With Quick Selection Tool (shortcut: w) select the part you want to keep.
2) Use Select > Refine mask (shortcut: ALT+CTRL+r) and adjust radius until it looks perfect. Use this mask to couple a mask layer on to your background layer (unlock it first). Put a layer of perfect white underneath it.
3) If any trouble areas still exist, use a Wacom digitizer or similar tablet device, to manually take care of it.

Do you want shadows or not?

On first, too much white space to left, not enough below.  On second, way too much on left.  Logo on black plastic part.  Both white areas not pure white.