Hi,
I made this last year for Christmas presents since like you, I fell in love with it in Italy. I used 2 gallon jars, but could have gone with the one gallon.
Some tips: I used vodka because I could not get grain alcohol like they use in Italy. The lemons over there taste a little different than here because of the soil. If you can get Meyer lemons, those are closer in flavor.
When you are tasting it, it will not seem sweet enough before the soaking process. Don't add more sugar or it will end up tasting like syrup. If you use lemons from the grocery store, they need to be scrubbed to get the wax off.