I seriously need help with my driving itinerary!

For starters Google map from stop to stop for drive time and add 25 %. Heritageireland.ie website has information on many sights including average visit times.
You cannot do all that you are suggesting on several of the days. In particular the 21st. Trim and Newgrange are north of Dublin and Glendalough is south. That is two days worth of sightseeing.

It's tough but you have to prioritize and cull stops or add more days to your itinerary. Good luck.

Not sure you will make your 3 pm walking tour on the day you arrive. You are only giving yourself 2 hours from landing to the tour. This assumes no delay in departure, no delay in getting to the gate, you have to clear passport control, receive your luggage and get to the city centre. I would be flexible with that one

Kilmainham gaol: make sure to pre-purchased you tickets on the web before you go.

We took a similar trip (Sep. 19-Oct 4) five years ago and I totally understand both your desire to see everything and your befuddlement over how to best make that happen. That being said, I do think you have an unrealistic view of how much time it will take to get from place to place and how tiring this kind of travel can be. A few things I can point to right away--your idea of doing New Grange & Powerscourt/Glendalough in the same day is unrealistic, especially since you intend to continue on to Kilkenny. New Grange was one of our favorite stops and definitely shouldn't be missed, but perhaps you can do it at the end of your trip since you'll be traveling from Northern Ireland to Dublin. You'll need to allow at least half a day for the stop though. As for doing both Ring of Kerry and Dingle Peninsula, I think you may find that to be a bit much for your time frame. On our 2012 trip we opted to skip the Ring of Kerry because friends had told us that, as Oregonians (fellow Portlanders, actually) we had seen similar vistas on the Oregon coast. We loved the Slea Head Drive in Dingle--one of our favorite places on that trip. We made a second trip to Ireland in 2015 and got to drive the Ring of Kerry. It was beautiful and did remind me of the central Oregon coast--but offers so much more. It's hard to recommend one over the other, but if pressed I think I would opt for Slea Head this trip and plan a return visit to include the Ring of Kerry then. I would also recommend skipping Waterford--there isn't enough to see to justify the time. And keep in mind that both the boat tour of the Cliffs of Moher and the ferry ride to Inishmore are very weather dependent--if the seas are rocky, nobody sails, so it's good to have a backup plan. I don't see an overnight stop on the 26th--are you staying in Doolin? And what about the 29th--are you staying in Derry? I think you should be able to refine your itinerary to include most, but perhaps not all, of the things you want to see and still be able to enjoy the experience--it will be fabulous! Good luck!

PJ, I really appreciate your detailed response. Yes, and to all that responded, I realize my initial plan is way too ambitious. I'll trim it back.