Black line on sim's face?

I checked the DDS version of your shadow map and it appears the white sections on the alpha map are too large. Here's a good tutorial if you need one.

And I have some tips for you about your mesh. Looks like you modeled it in Marvelous Designer and you modeled in Tris. It's always best retopologize your mesh as MD produces messy topology and often the MD meshes are way too high poly anyway. I've got a PDF with instructions as well as videos here if you're interested in learning to retopologize your mesh. Please note that the instructions are more about using Zbrush but there are other ways to retopologize your mesh. Mauvemorn has videos here.

You need to delete the body parts that your mesh is covering up. There's no purpose in keeping them, they add to your polycount, and there's always the issue of clipping that can occur during certain animations. You should close the hole in the top of the pants, as well. The bib portion is double-layered, and that's fine, but close the hole right about where the pants' waist is. I hope that makes sense.

Edit: I just noticed that many of Mauvemorn's videos have been hidden and only the Zbrush one is available. So, your options for retopologizing a mesh if you don't have Zbrush are the following:

1. Use MDs remesh function. It doesn't always yield good results, however.
2. Use MDs manual retopology tools. Can be challenging if your pattern pieces are weirdly shaped.
3. Manually retopologize in Blender. You can use Retopoflow (there are videos on YouTube explaining how to use Retopoflow) or you can just add a flat plane, make it into either a small square, line it up with the corner of one of your MD pattern pieces and start extruding to shape it, or add a flat plane, make it roughly the same size as one of your MD pattern pieces and add edge loops with ctrl + R. You'll need to shape the flat plane so it's the same shape as the flat pattern piece exported from MD. 

After you have new, retopologized flat pattern pieces you can then use the shape key and surface deform modifier functions that are explained in the file I shared.