I do not get it why the Caighdeán went for Éire as the nominative for Ireland but Albain, and not Alba, for Scotland…
It looks like a very similar situation – where in native speech in both cases dative form (Éirinn and Albain) is used, and the proper nominative (Éire and Alba) is archaic.
Perhaps because Éire rather than Éirinn has been on Irish coins since 1938.
Spoken Irish uses an "epenthetic vowel" in certain consonant clusters. You can hear this in words like gorm (http://www.teanglann.ie/en/fuaim/gorm), feirm (http://www.teanglann.ie/en/fuaim/feirm), bolg (http://www.teanglann.ie/en/fuaim/bolg), ainm (http://www.teanglann.ie/en/fuaim/ainm), airgead (http://www.teanglann.ie/en/fuaim/airgead).
This process has persisted in English as it is spoken in Ireland - Irish people pronounce"film" as "filum", for example.