In the original manuscript for Alma 58:3, Oliver Cowdery initially wrote these; but then he immediately corrected the these to those by overwriting the e with an o (the level of ink flow for the overwriting is unchanged). We have many examples where Oliver mixed up these two demonstratives (most recently in verses 11, 16, and 20 of the previous chapter). For a general list, see under Alma 3:25.
In this passage we have another example of the mixed gerundive construction: “to the maintaining those parts of the land”. For some discussion of this complex construction, see under Alma 55:19 or, more generally, under gerundives in volume 3.
Summary: Accept in Alma 58:3 Oliver Cowdery’s virtually immediate correction in 𝓞 of these to those.