If it was out of the ordinary compared to the usual enterprise rock and roll ride, it was worth complaining about
It sounds fairly serious, given the conductor (19:00 is an NIR train) didn't really seem to care you should report in writing to the Rail Safety Commission what happened (info@rsc.ie). Under EU law it doesn't matter which side of the border an incident happens the RSC in Dublin can investigate
I wager it got better once you left Dundalk
In such circumstances you are entitled to pull the communications cord,
http://www.rsc.ie/uploads/RSC/Passenger-Guidelines.pdf
Despite the spin there is much to be done to improve safety on the rail network and the attitude of the conductor and lack of urgency in dealing with the circumstances is worrying. Long standing policy is 'stop and examine' and failure to apply this has had tragic results, Eschede in Germany for instance