The Republic of Ireland's currency was the Irish pound until 2002, when it was replaced by the euro. The Irish pound was often called the punt in English too.
Neither do I, even after cranking up the sound on my external speakers — but I'll allow that "we do not use the Irish pound" sounds more like a sentence one would actually hear than "I do not use the Irish pound."
No, the pound sterling is used in Northern Ireland. The same currency is used throughout all four countries of the UK.