First of all there is no need to "Interpret" Acts 2. It says what it says. All Peter is trying to do is to get the Jews to accept Jesus as their Messiah; to believe that He is their Messiah and that they killed Him. There is no mention of salvation through the shed blood of Jesus that covers sins.
With all due respect, what exactly do you consider to be the whole message of Jesus!? Peter is proclaiming Jesus here and the message is a single unified message. He was attempting to get the Jewish population present to recognize their error, but at the same time he's preaching the Messiah from the Messiah's perspective and not from the Jewish perspective of the Messiah which was entirely in error.
Second, according to my Bible the people there in Jerusalem were mostly Jews and Gentile proselytes celebrating the Passover (visitors from Rome “”(both Jews and converts to Judaism)””. Gentile of other religions would not be there to celebrate the Jewish Passover.
Ironically, here, you admit your own error. Perhaps they were mostly, but mostly is not all even as you just admit. :)
In all seriousness, proselyte is the word render convert in the NIV. It literally means a stranger or alien in the sense of someone newly come to the faith.
As far as your last remark, I see you have something against teaching the scriptures from a dispensational viewpoint. Obviously you are in the crowd that takes all the scriptures and blends them together and comes up with a harmonized gospel that man has written to fit a theology that man thinks will save him.
Actually, most would consider me a dispensationalist. I try to avoid the jargon, but clearly there are appointed times for certain rules of God.