I really do like your one-dimension range band method for space combat.  It's about what i can hold in my head when DMing after a long day at work. 

Are most starship weapons infinite range when dealing with combat scale?  That's one thing i couldn't find.

As far as the battlespace is concerned yes. Anything on the board can be shot. If for some reason I was running a battlespace with ships 30 bands apart perhaps I would say attacks are impaired but I can’t think of a scenario where that’d be necessary.