@2382680 , agreeing with the comments from @Critter-3 to the general theme, I still am not quite sure of your earnings situation. So , let me put down what I understand --
(a) you a US person ( citizen ), are living in Italy
(b) you wish to take advantage of foreign earned income exclusion -- because your earnings are foreign, , you have a tax home in Italy and presumably you meet the requirements of Physical Presence Test ( form 2555) ;
(c) you also wish to NOT participate in the Italian equivalent Social Security and therefore because of the Totalization agreement between US and Italy, you wish to pay FICA taxes to the US only.
Assuming the above describes your situation at hand , the easiest would be to :
1. enter your gross foreign source income ( i.e. before taxes ) as if you are self-emplyed -- Schedule-C. This will automatically prepare a Schedule-SE for the FICA/SECA taxes ( at 15.3% on most of your gross income);
2. You also have to prepare a form 2555 for exclusion of the foreign income
3. Get a certificate of coverage from US -SSA to show to Italy ---- see more details here -->
https://www.irs.gov/government-entities/federal-state-local-governments/totalization-agreements
Does this cover your query ? Is there more I can do for you ?
pk
