When reporting a data error, include the page URL of the player or club — it gets fixed much faster. Known source-data issues are listed on the coverage page.
A weighted sum of countable match actions. Every weight and a worked example are on the method page.
Only a limited number of leagues publish player-level action data. If the source has no action data for a league, DS cannot be computed for it. New leagues are added as coverage allows.
Fair enough — and because the formula is public you can point at exactly where you disagree. Tell us which action weight looks wrong and it gets reviewed; the weights were calibrated against real data but they are not final.