How do I get the same app to open differen files in different spaces?

AFAIK, there's no generic means to tell an arbitrary app to open an arbitrary file in a window in an arbitrary space. Which means you're left to open the files in whatever space the app is operating in, and then drag the windows where you want. Using Exposé such as is available in Sierra is handy for this, as you can do it all from one view; drag the specific windows from the main view into the spaces at the top of the view.