Alignment and distribution doesn't work.

[rich2005]

Layer groups tend to screw the align tool up

Having a look around, remembered this plugin arrange-layers-0.2.py dated 2012-11-30 see:http://sourceforge.net/projects/gimp-tools/files/scripts/

It might work for you, your first sceenshot does not show the layer structure, so a guess.
Set the position of the layers horizontally
Make only the layers to space out visible
Make a selection, same as your bleed margin
Apply the plugin Image -> Arrange layers -> Spread -> Vertically

example: https://i.imgur.com/VUvtCzb.mp4