Matilda, you did a very good job. lylaphoenix has made the same comments I would have made. There are a few more things I would change further, but I think you captured 90% of the song's meaning.

1100 (or Millecento) I would translate as "family car" or Compact car" or Sedan (Saloon if you are on the other side of the pond from me)

This:
"la notte che le pantere
ci mordevano il sedere"

"Le Pantere" were at the time (and maybe today, I haven't been back to Italy in a long time. Long story) the Carabinieri Cruisers or Police Car. They are called "Pantere" because they were black like the Carabinieri uniform.

The actual Police cars were called "La Volante" as in the "Flying One". Short for "Squadra Volante" or Flying Team.
But the "pantere" reference here is about the Police cars chasing the demonstrators and biting their ass.
You can loosely compare the Carabinieri to the FBI or the Marshall Service in the US, but with elements from the Highway patrol, etc. It's a quite unique Military force. Yes, they are also Military Police. Their members are Armed forces.

Funny story: I was a Lieutenant in the Army. As an officer I was the lowest of the low. But in the Carabinieri a Lieutenant is a really big shot. Most of the hierarchy are NonComs like Sergeant, etc. So I loved to get stopped by the Carabineri when I was out in civilian clothes and see how they would quickly change their tune and start throwing sharp salutes at me as soon as I gave them my Military ID :) What can I say, I am easily amused. I was 20 years old. Some of them were in their late 30's.

If you are not a native speaker, I am very impressed by your work.
Maybe I'll give it a shot someday and you'll be more than welcome to borrow whatever you want for yours if you think I might have done it better.

Grazie per aver tradotto questo bellissimo testo, anche se avrei un paio di correzioni da suggerire:

"Convinti che fosse un gioco a cui avremmo giocato poco" lo tradurrei come "sure that it was a game that it would'nt last long" perchè se dici "that we don't play often" stai dicendo "un gioco che non giochiamo spesso"

"we let ourselves be massacred" vuol dire "ci stiamo lasciando massacrare"
se si vuole dire che CI state lasciando massacrare, la traduzione è "you let them slaughtered us"
quindi io scriverei "you let them slaughtered us on the pavement in good coscience"

"give a damn" significa che te ne importa. Per dire te ne freghi la frase corretta é "you don't give a damn"
ma in questo caso più che "anche se ora non ve ne importa" credo De André intendesse dire "anche se ora fate finta di niente"
che tradurrei come "you walk away from this" (praticamente "ve ne state lavando le mani")

"quartieri" è "neighbours", non "quarter"