The pronounciation of "againn" here, is it meant to sound like "ag-wing" rather "ag-win"?
Yes, ainn can pronounced with an "ing" sound.
FGB doesn't have a pronounciation for againn but you can hear the "ing" sound in the entry for álainn
No we don't because all the potatoes have rotted in the field and we have to give our eggs to the English landlord.
In English, this comma ought to be a semicolon. Would you also use a semicolon in such a way in Irish? For that matter, should compound sentences connected with a conjunction in Irish be separated by a comma, as they ought to be in English?
Another very useful sentence! I've noticed that the more applicable a sentence is to real life, the less useful it is to describe Pól's activities. Ah, well.
Can one say Táim ocrasach, instead of Tá ocras orm?
Yes — ocrach would be another adjectival option — but I don’t know if it would be preferred.
It has always felt to me that the noun + preposition phrases are more natural than the "be" + adjective options.