First, congrats on the excellent cygwin debugging and the test module build! It’s a big day! 
You may want to look at the thread below, especially from the linked post down (on Linux initially, but it speaks to some of the same issues). I’ve been thinking of trying VSCode for Rack on Windows and am about to start prototyping a V2 module, so if that doesn’t work I’ll give it a shot myself, and if it does work please post the fix so that I don’t have to figure it out myself
Edit: this article, linked from that thread, looks super-comprehensive, and may be useful beyond just the rack.hpp issue.