The contraception vote happened in July, two months after the Dublin/Monaghan bombings. You are confusing it with an earlier set of bombings in late 1972 when FG were in opposition and there was a vote on the Offences Against The State Act...
Fianna Fáil would certainly have dominated things through the 60s (but then they dominated things through the 60s in any case under STV) simply because the opposition was split, and split in such a way that you had one party to FF's left (Labour) and one party largely to FF's right (the...