So, about the nature of Giorgio... (spoilers)
Is he supposed to be undead?
I mean, he's been living off water droplets for 40 years and maybe the odd cockroach here and there, yet he manages to move like a strong person, rip off his own thumb without dying of blood loss, and have a melee encounter with a 40-something guy and almost overpower a group of 3 people. He also seemed to be really witty and stealthy for someone who's never had any training in those areas.
Like, imagine how weak you would be if you hadn't seen sunlight ever in your life, and sustained yourself with a few water drops each day. You would be skeletonized, and more realistically, probably dead within a year or so.
Or did the mother die just a few days before the americans arrive?