2D top-down sorting layers. How to use sorting group?

I have a Script that sorts stuff in my game depending on the y-axis, it's attached to my character and any object I want to render both in front of and behind my character, it looks like this:

Code (CSharp):

1. private SpriteRenderer spriteRenderer;
2.  
3.     void Start()
4.     {
5.         spriteRenderer = gameObject.GetComponent<SpriteRenderer>();
6.     }
7.  
8.     void Update()
9.     {
10.         spriteRenderer.sortingOrder = (int)Camera.main.WorldToScreenPoint(spriteRenderer.bounds.min).y * -1;
11.     }

Super simple. However, now I have more advanced character, that has several children (all containing sprite renderers) that are body parts, probably 30-ish body parts. As you can imagine this screws up the system I have been using, since I need to use the individual sorting layers to make sure the character is rendered correctly.

I've been playing around with a sorting group on the parent of the character with more or less the same script but no luck. Surely there must be some way I can solve this?

Edit:

Some stuff worth mentioning:
Sorting group almost works but I dont fully understand it. In order for it to work I add it to the parent, and set its sorting layer to the one that all other object which sort automatically are on.
This kind of works, but for some reason I need to set the initial value in the sorting group to 290-ish, and if I re-size my screen that value has to be changed. Maybe someone that understands sorting groups can make sense of that.

Example of what I mean:

 

Might have solved this, let me get back to you guys

 

Did you solve it ? I have a similar issue myself, your solution might guide me.

 

The problem was in my sorting script, and setting the sortingOrder according to the cameras position. If you have a sorting script paste it here and I might be able to help

 

In your workflow, you have to individually add the script to every object that would need to dynamically sort at runtime?
Sorting groups apparently are a little "buggy".