Ecuador grounding an ungrounded house
Ecuador is kind of on the fuzzy edge of 120V/NEC territory, so you might have Euro 230V in places. 

The ACSR service drop is providing netural, not ground.  If the neutral wire breaks, it's perfectly normal for neutral to float up at hot voltage.  That's why we insulate it.  The problem with bootlegging ground off neutral is now, all the grounds in the house are also energized. 

So you should fit a normal at-the-house Grounding Electrode System, to whichever level of detail you wish to replicate NEC standard practices. I don't think your AHJ is going to stand on two ground rods and AFCI/GFCI for everything. 

Although, given the local fetish for removing ground pins, circuit-level GFCI protection is a VERY good idea. While it does nothing to protect equipment from ESD, GFCIs do everything to protect humans from shock, and serves that purpose better than grounding actually. However it is vital that ground not be bootlegged after a GFCI; doing so utterly defeats GFCI protection. 

As long as the #12 is on an outdoor pole line, I couldn't care less. That's typical of the downsizing you see on service drops - many a 100A service has #6 aluminums, a comparable downsize.  If it's inside walls in any way, then yes, that's unacceptable and it's time for appropriate sized wire. 

Seriously the money spent upsizing the service drop should be spent on GFCIs instead. I trust you know how to use LOAD to protect an entire branch circuit from one device, though, don't protect too much or the cumulative tiny leakage from many devices will cause a nuisance trip.