I have make a quick tutorial on how to make billboards using the code already included in the shader code examples. It's pretty easy, actually.
https://mrlevrocks.itch.io/mode7/devlog/812974/how-to-add-billboards-to-mode-7-s...
Normalizing depth might be a bit harder but what you could do is pass the calculated height from the draw event into a defined variable and then set that in the end step event. Tell me if that works.