Hello from Wisconsin,
All these weird rental prices are due to Covid. Amazing.
car rentals...First step...Book a fully cancelable rental car.
Consider exactly when and where you want the car. If you are renting to get to the west coast, take the bus there and rent in Galway or Limerick. Or where will you end your touring? You could possibly drop the car at the last city you visit and bus/train into Dublin.
Now go shopping.
Start with AutoEurope. You can do their website. It gives you a place to start. it is not the dumbest thing to call them. I have had great luck with extremely knowledgable staff.
Shop Europcar. Once again, you could talk to someone there. And if your current offer is $40 per day, tell them you have a reservation for $37. See if they can beat that.
Never cancel a rental until you have a firm reservation in place with which to replace it. Doing the reverse could leave you empty handed.
Go back to Autoeurope every week or so to see if prices have changed. Once, I landed a Valentine's Day special even though I was going in March.
Good luck,
wayne iNWI