Extrude surface normals

Hello GH Community,

I am having trouble figuring out the best approach for this problem. I have some triangle surfaces and i would like to add thickness too. I have been able to extrude them to their surface normals using the evaluate surface and surface closet point components but i don't think that solves my problem unless i am missing something.

1. I want to have mitered angles. As you will see some angles are open and some overlap. Is there a way to correct this so the extrusion is split directly in the middle of these results, no matter the thickness of material?

2. also, is there a way to concurrently have the angles along the perimeter extrude straight back in the Y direction whilst also correcting the open/overlapped angles?

Thank you in advance for your help GH Community.