Firstly, your English is 100% better than my Italian, so no apology needed
Sorry no using a 64bit OS will not help, as FPSC is still a 32bit application and no matter how much ram you have it will still not alter the fact it is a 32bit application, sorry
My London Pack video shows a map that uses all the map grid and starts at layer 0 with tower blocks reaching to around layer 18 (top layer is 19) with quite a lot of entities etc in the map. This ran fine in v1.17 with lightmap quality set at 25 using less than 1.3 GB memory.
My tip is lower your lightmap quality by about 5 and use a few more dynamic entities over static ones as these do not effect the light sources. I have also noted that the memory required to build the map can vary a bit the more you test/build the map and a reboot of your PC then build can get you back under the 1.85 limit.