Yeah, their LPK's are very questionable. Most of the parts are alright, but their trigger and hammer leave a lot to be desired. Feels like you're dragging a cinderblock across hot blacktop.
I used one in one of my builds and while I don't think it was as thick as yours, I can say that some 400 grit sandpaper and a few minutes rubbing the parts back and forth on it sure didn't hurt it any.
Does your hammer have an SS marking on it too?
I've noticed them in a lot of different brand kits.
As for the lower, I have a couple Anderson lowers. Being made in my home state, they're usually readily available. I guess I still should buy a Doublestar lower just to have one.
I figure if worse comes to worse, since the parts from the factory have never traveled in interstate commerce to me, the fed government doesn't really have any official authority over them as long as it's only involved in intrastate commerce. Or so maybe one could argue.