Pages multilevel bullet spacing
Update Pages to version 5.2.2 (1877). I don't know when they've added the following functionallity, but with this version you can do your changes manually one time, and then update the bullet list style as follows:

Open the Bullet &amp; Lists drop down pop-up. Notice that there's an update button next to the bullet list style name, which is marked as 'changed from default' by an asterisk:



You can either press the update button, or click on the arrow next to it and select 'Update stlye' from the popup menu (featuring other options like clear, rename or delete):