I see you are asking this in multiple forums. Ruger CS probably knows the answer. I have no complaint with the sights on my GP100MC, but I know the front sight is different; dunno about the rear.
No, adjustable. The insert, which I gather is what you're complaining about, looks the same as on my other Rugers, except for the Blackhawk .45 not having the white outline.
Ruger say's they try hard to source their parts from the US, so I'll take that as a no they don't make their own and who knows where they get them as it would seem they don't really want to say.
Like most firearms manufacturers, the small parts would be outsourced. Heck even some large parts are. Ruger's invest casting division actually produced raw frames for other gun makers. I know at one point a machine shop in NH was making receivers and tons - literally tons of small parts for a number of firearms manufacturers. A small shop up this way was, possible still is, making the hammers for Colt's SAA's.