Then again, with respect to (1.), Epicurus does discuss the creation of worlds (EH 45.5), so perhaps Lucretius is merely referring to the creation of a world-system, and not the universe as a whole. (I am imagining – as a reasonable, modern analog – a contracting, pre-solar nebula that flattens into a protoplanetary disc that then rotates around a hot protostar until the rotating matter accretes into planetesimals that eventually develop into different worlds.) I might have been getting stuck on the idea that "nature creating" refers to a universal beginning rather than a local beginning.
"...such a world may come into being both inside another world and in an interworld, by which we mean a space between worlds; it will be in a place with much void [...] this occurs when seeds of the right kind have rushed in [...] little by little they make junctions and articulations, and cause changes of position to another place [...] and produce irrigations of the appropriate matter until the period of completion and stability, which lasts as long as the underlying foundations are capable of receiving additions." (EP 89.2-90.1). So Epicurus does identify a preceding stage of instability, per kosmos.
Therein, particles moved from a stage of "falling raindrops" (DRN II 223) "first", "and gradually grew in size by the aggregations and whirlings of bodies of minute parts" (EP 90.8-91.1). At some point "stability" is reached. I am comfortable with "creation" when taken as the development of a system of celestial bodies ... however, I still don't see the need for the "swerve" to create this arrangement. Perhaps one particle re-bounded from an "interworld" and started a cascade amid the cloud of "falling raindrops" (rather than one drop in the cloud "swerving" into another).
Overall, I question whether or not the "swerve" served any other function for Epicurus besides providing a rational counter-point to Democritus' determinism. Epicurus explained how world-systems develop to Herodotus and Pythokles without discussing the "swerve", and he explained choice and contemplation to Menoikeus without referring to an atomic "swerve". I am speculating that the declinando or clinamen in De Rerum Natura – described as a world-building and thought-forming agent – was more of a poetic embellishment by Lucretius than a reflection of Epicurus.