Low 1-C is fine by me. We already assume that the space in which spacetimes are displaced is 5-D, at present. Add that to the space in question here being explicitly described as infinite and the worlds as "small" compared to it, and you have a fairly straightforward case.
I don't think the 2-A option is terribly logical either, after mulling it over: 2-A would imply that universes in KH are displaced over 4-D space, which doesn't work when parallelism of any two objects by definition requires an extra axis: For two line segments to be parallel, you'd have to set it so they wouldn't touch regardless of how far they are extended, which wouldn't be possible if they stood side-by-side in 1-D space
as in here, meaning you would need them to be displaced over a plane. Same thing happens with planes: For them to be parallel, they shouldn't ever be able to meet, so you'd need them to be displaced over 3-D space. Generalizing that to the 4-D case, spacetimes would obviously have to be displaced over a 5-D region (This works by definition, too: If they're different spacetime continuums then obviously they can't share the same space, in the way 3-D objects exist around us for instance)