Elegant shift between alliteration and assonance.

In Eldarissa valto meant 'good luck' and Valar 'the happy folk'. How do we interpret valto in a late-source context, where Valar  means 'those with power'?

Thanks for the kind words:) Yes, it is a (slight) problem that there seems to be no neutral word for 'luck' or 'wyrd' as it were; our examples seem to be either positive tending towards 'bliss' or negative (or at least that is my impression).
Valto in a "modern" context can still mean 'turn of divine power expressed in fate/luck", I think.

Isn't umbar at least a rough equivalent of "wyrd"?

Rough, yes - but I seem to recall it carries more negative than positive connotations. In my mind at least wyrd is neutral.