Having had a similarly frightening (though different) experience some months ago when a motorcyclist hit my car and flew 20 metres down the road (he was miraculously able to stand afterwards) I kind of understand the vulnerability you feel when standing your ground here. My case was a lot more debatable as to where the blame lay as I was swerving to avoid someone else and the moto guy was doing the normal million miles and hour. However, the standout points that no one seems to have picked up on are for me;
Actually the police behaved very professionally (I had about 6 of them as it was in Alta Palermo). They didn't take anyone's side, spoke to witnesses, and were non agressive and non-judgemental in my case. It appears this is true of yours.
In a contested accident the police impound both your cars / vehicles as security for costs (in my understanding). This gives you a very strong reason not to back down if you are in the right, as damages are to some extent guaranteed by their assets.
I started driving much less aggressively after my accident as I always had it in the back of my mind what shit would have transpired (possibly custodial) had the guy been killed. I have now reverted back to driving like everyone else here(though obviously as a brit I think I drive better), as driving slowly seems to provoke more agression than anything else.
You were very unlucky to meet a middle class kid that could actually throw a punch. My experience is that they are normally too worried about ruining their clothes (this does not apply to kids from the villas of course).
Your story also makes it clear that the medical care in extremis is very high quality and professional. I have had a few minor accidents, stitches, rib injuries etc, and have been treated both privately and in the public system (when I was bleeding profusely). Certainly compared to the UK, the healthcare seems to be excellent.
I'm not trying to diminish the gravity of your experience in a any way, just picking up on some of the positive points that you relate that otherwise the naysayers who predominate on this site will ignore. Having spent a lot of time in real 3rd world countries in Africa, India etc, I am sure things would have been different there.
Hope you make a speedy recovery!
I also feel like they sided with the father "what do you expect a son to do?" is no attitude for a cop to have - they should be upholding the law, which says you shouldn't harm another person. They didn't seem too interested in seeing justice served or stopping this from happening again. 