Nice translation.
Line 2 (not counting the refrain) and its repetition as line 10 seem to me more like "You kept me behind all others" or "you kept me later than all others" than "You kept me from all others at last", because there's nothing in the line that can possibly mean "from". Maybe she's saying "I lasted longer than any of your other girlfriends."
Line 7 is "a young Campbell in its inside " ("oirre" is a weird way of writing "air a" in this line, this is quite clear since the prepositional pronoun oirre wouldn't lenite the s or siubhal, but "a" (3rd person singular masculine possessive pronoun) does and of course refers back to the heart mentioned in the first part of the sentence (line 6).
Line 8 has "and" at the beginning (that's what "'s" means) - lines 6,7,8 and 9 are all one sentence (as are lines 2,3, 4 and 5).
This is simply my translation, other translations of Fowlis' songs are available online.