Ditto = Destiny Knot
Ralts = Everstone
Destiny knot does not affect natures, Everstone passes natures and abilities but not 100% of the time. Get 5x party full of ralts and compare in comparison. Everstone should most definatly pass nature, if not then I don't know why. It always does!
When you breed, you have 3 possibilities for the IV of each stat for
the baby. The first is that the child will have the mother's IV for
that stat, the second is that it will have the father's, and the third
is that it will randomly choose an IV for that stat. When breeding
without the knot, three of the IVs will be inherited from the parents.
So if you have a set of 6 IV parents, the child might inherit the HP
and Def from the mother and the Sp. Atk from the father, resulting in
a 31/x/31/31/x/x child. With the destiny knot, five are passed down
instead of three. In the example, we might inherit the Sp. Def and
Speed from the father as well, resulting in a 31/x/31/31/31/31 child.
They don't pool. If a stat is passed down, it goes to that same stat,
i.e. if the mother's HP is passed down, the child's HP will match the
mother's. It won't go to a different stat or be added to a total
amount to be distributed between stats.
I know this from extensive research on ev and iv breeding from watching youtube channels over and over.
Hope I Helped and goodluck to others!