1. F-117 is a primitive aircraft that was designed in the 1970's. Everything from metallurgy to avionics was "quaint". The design (shape) was based on readily available research that anyone could access.
2. Youtube based threads suck.
Also, for low observable shaping to work, the manufacturing process needs to be highly precise. If parts of the fuselage fit together poorly, there will be seams that show up on radar. This is one of the reasons that no other country has ever produced an aircraft that is effectively invisible as the F-117, B-2, F-22, and F-35 are.
As your first point kind of suggests, the problem with stealth technology is not that the principals are secret, its that the principals are extremely difficult and expensive to exploit.
As a wholly separate aside, the US maintains a lead in radar technology that's almost as significant as its lead in stealth technology (and those two items are obviously very closely linked).