NoScoE30 has agreed to reprofile the threads to be more like the design on a USP barrel so I can mount my Obsidian and not chew up o rings or have a sub-par seal. He has some fancy lathe (see picture below) that he's going to do this on and he's charging me next to nothing. This is why I love this forum! I'll post pics when the barrel comes back for the sake of comparison.
My thanks to all of you for helping me solve this problem and especially to those who reached out and offered to do the work for little or no cost.