My question involves criminal law for the state of: California

Okay, so here is what happened to me two Friday's ago:

My brother-n-law and another driver got into a fight which I was stuck in between from trying to hold my brother-n-law back. Punches were thrown for a good 10 seconds it seemed (started from the other driver) and for a brief moment they separated. As soon as they did though, the other guy swung a punch at me but missed. I looked at him in surprise and at that time he said, "Oh you mother******s want to jump me!?" And as he said this he was already getting ready to throw another punch at me.

As he stepped toward me, with his right hand about to come at me, I reacted and ducked his punch and threw a right fist at him as well. I knocked him down and once I saw he was disoriented, I didn't do anything else but call 9-1-1 to let them know this guy just attacked my brother-n-law and myself.

To make a long story short with the sheriff's there: I was handcuffed, put in the back of a car, taken to the station (never was I told I was being arrested nor was I read my Miranda rights). Once we got there I asked the sheriff what was going on. He said the following:

"Because [they] weren't there to see what happened and when they did get there, the other guy had the injuries, he had the right to place me under citizens arrest...we are citing you for battery...it will most likely be charged as a misdemeanor."

Once in the station, they took my shots, my finger prints and placed in a holding cell for 6 hours and then released around 6 a.m.

My questions are:

1. Can they arrest me without informing me I am under arrest/citizens arrest?

2. If I was placed under arrest/citizens arrest, can they do this without reading me my Miranda rights? And can he do all of this without asking me my side of the story as to why I hit the guy?

3. How do I prove I was defending myself against this guy with no witnesses other than both families that were there?

-The only thing I have going for me is that I only hit the guy once to get him to stop. The only proof I have with that is the one, and only, injury I have to my right pinky finger.

Sorry for the long thread. That is actually the short version of what happened too. Imagine if I wrote the whole thing...

Please advise though. I would greatly appreciate any and all help. THANK YOU!