Ticketing & Getting around Dublin

[91101_GNER]

Hello, I'm from Newcastle in Britain, and I'm travelling to Ireland in a few weeks. Coming from Birmingham overnight on the ferry to Dublin, down to Cork, back to Dublin (0700 Hueston - Cork and 10:30 return). I'm then getting the 16:50 to Belfast, and returning the next day on the 10:30 ex-Belfast Central.

My ticket for Dublin - Belfast was €90, and I believe is closely equivelent to what we have in England as a First Open Return (Outward on day one, return valid for one calendar month, travel by any train along any permitted route) is that generally speaking right? If I miss one train I can just hop on the next? What about break of journey? I'm thinking of possibly getting off at Drogheda for a bit of photting, before completing the journey to Dublin for the return ferry crossing.

Obviously I need to get from the Ferryport to Hueston (got about an hour to do this providing the ferry is ontime) and then from Heuston to Connolly. I know that the Luas is the best option for Heuston to Connolly, but what about from the Ferryport?

I'd just like to say that this site is invaluable!