Re: Step 1 done
Which is why physicists prefer not to think about it and stick to systems of coordinates. "In what" is a metaphysical question.
Well, systems of coordinates are evidently artificial though practical, so the quest to find the (most compressed?) model of spacetime covering all empiricial evidence (and beyond), in particular, naturally giving birth to the Standard Model, goes on. This isn't a "metaphysical" quest.
Saying that "physicists prefer not to think about it" is inherently wrong. It's engineers who prefer not to think about it.
See also this writeup: Space is Meaningless
The postmodern unobservable and extravagant "multiverse" sure is metaphysical, or worse: It sounds like an alibi for being impatient and unwilling to do the hard work while still staying in the limelight.