Please provide suggestions for my itinerary. Thanks!

That is an intensive itinerary with a lot of driving....

Are you coming off a long haul flight from USA? If so driving from Dublin to Donegal on your first day when you are still jet lagged (at least four hours PLUS any stops) is foolish... In fact you've not really built in any time to recover from jet lag.

One night in Galway isn't going to allow much time to see anything of Connemara and its stunning scenery, although it does break up the long drive from Donegal.... Stop near Cliffs of Moher (much over rated and Slieve League in Donegal is much better!) - suggest Doolin area...

Do Dingle before Killarney (avoids doubling back on yourself. Also one night doesn't give much time. I'd be inclined to cut the night around Cliffs of Moher and add to Dingle. You can do Cliffs of Moher on the way to Dingle. It's a long drive from Galway but doable in a day.

What time is your flight from Dublin. You need to allow at least three hours for the drive and then time to drop off the car etc.

Thanks so much for the advice. We are staying in Dublin a couple of days at the beginning, sorry I should have included that. Just to be clear, you are suggesting I remove Galway and add Doolin? Also, our flight leaves coming at 4:00 p.m.

Definitely switch the order of Killarney and Dingle. I personally would not be comfortable with having to drive 3 hours the morning of my flight home. The M50 ring road can be a disaster no matter the time or day. The car rental return at Dublin Airport is remote. That is, you have to shuttle to the terminal. With a 4:00PM departure time I would want to be at the rental return location by 12:30PM. At the risk of adding another "one night stand" stay in Kilkenny the night before? It would put you 1.5 hours closer.

Can I suggest Killybegs as a place to stay in Donegal? Good access to the Slieve League via boat tour and by driving up to the visitor center to see it from above.
I agree skip Galway and stay in Doolin, flip Dingle and Killarney.
I assume you're doing the Ring of Kerry.
I'd book my accommodation right quick. With a car, your options are increased, anyway. This may decide things for you. Look at the smaller towns on your route, and use Google maps to find hotels and traditional B&Bs or the map feature on AirBnB.

Thanks to all for the wonderful suggestions, I really appreciate your time!