I've been playing with this some this evening. I can get the font size changes I set for each level of indent, but it doesn't indent. As soon as I increased the indent level using the button on the tool bar, the number changed to the next sub-level number. I haven't worked with using the list styles, so I might be able to change it there. I'll see what I can do this weekend.
But, after all of this, I think that you can achieve what you're looking for by just applying the legal list style then indenting either with the tool bar button, the Format > Text menu or ⌘]. I have used keyboard commands for this in AppleWorks for years & I think it's just a little easier there. I can create a new line using ⌘ L or ⌘ R, putting the new line less or more indented. The indent level of an existing line can be changed with keyboard commands, similar to Pages ⌘ ⇧ L or ⌘ ⇧ R.
Peggy