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.
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.