Is performing Istikhara and being accepted into the customs police—along with the Islamic Fiqh Academy's fatwa deeming it permissible—an indication of its goodness?

Istikhara is performed for permissible (mubah) or recommended (mustahabb) matters, not for obligatory (wajib), forbidden (haram), or disliked (makruh) matters. If an action is permissible, then Istikhara is hoped to bring good, by Allah's will. However, if an action is forbidden, Istikhara is not prescribed for it; rather, it must be abandoned.