International driving permit

Yes.
Hurry up and go to AAA tomorrow morning to get one.
It takes 10 minutes and it costs $15 (unless you want them to also take 2 passport pictures for you, in which case it's a little more).

Yes, it's required and a good idea. Go to AAA and it's fast and easy about $15. plus $10. photo. Nothing terrible will happen if you don't have one, but if you encounter an officious jerk you could be fined.

Yes, its required for Italy. You can get one from any AAA office even if you aren't a member. They issue them on the spot and they are good for one year. You just need to show your current state driver's license.

Your car rental company likely will not want to see your IDP, and if you don't have any accidents or police interaction you'll probably never need to show it, but it will be good to have, just in case.

BTW, my eyes are really light-sensitive, and the local AAA's camera has an extremely bright light that flashes quite some time before the camera actually records the picture, so it kept getting photos with my eyes closed. It took lots of tries and took a lot of time, but I finally got a photo with my eyes rolled up towards the ceiling (not looking directly at the camera or the flash) -- looked really goofy, but then again, no one ever saw it. The permit is good for a full year, so if you return to Italy (or any other country including Spain & Austria that mandate IDP's) within the year, you're good to go.

You need to carry both your IDP and your original licence. The IDP is a certified translation of your licence, it is invalid without your licence.

redgie,

You may find it interesting to read this Thread.....

https://community.ricksteves.com/travel-forum/italy/international-driver-s-license-is-this-required