Chocolate-Covered Matzah Bunnies

Not being a theologian, I'm still confused about some aspects of Judeo-Christian traditions.  No, let me rephrase that, I'm absolutely perplexed.  Having recently been to both a Bar Mitzvah and a Catholic mass, it was clear to me that the similarities between the two groups are striking.  What in particular?  The ritualized call and response.  Hymns that immediately echo what was just spoken either by the leader or the congregation.  Stand up.  Sit down.  If the Catholics incorporated Hebrew into their service (besides the constant mention of Jesus) the two experiences would be nigh identical.

...Which brings me to Easter and Passover.  I just had a question, and maybe you know the answer, and if so, please fill me in.  Why don't Christians celebrate the Jewish holiday of Passover?

This has the potential to be a hugely complex question.  There are references in the New Testament which, and I'm paraphrasing here, indicate that the coming of Christ is the end and the beginning...that all things that were sinful and considered "law" before are eliminated due to his resurrection, as he has cleansed the world from sin.  To oversimplify, Jesus was a reboot and a replacement of the old operating system.  While it has roots in the historic methods, it supersedes all in the past in order to pave the way for the new order. 

OK, I get it, but then why does the Easter holiday float with the Jewish/Lunar calendar?  Obviously it is to signify that Jesus' last supper was a Passover Seder.  However, if the tenets of Jesus' own religion (as a Jew) are to be replaced, then the dates shouldn't matter at all.  It seems very arbitrary...like other things:

10 Commandments - yes...let's keep those

Keeping Kosher - no, that's ridiculous, ham for us.

Adam and Eve - Sure, original sin is for us

Yarmulkes - A hat, dictated by the Talmud?  That's not even the "Old" Testament.

Add those things to the abandonment of Hebrew - because it's clear that Jesus read and understood the language, however, most historians agree that the New Testament was originally written in a form of Greek.  Where did that come from?

I'm sure I'm not asking any new questions.  However, Christians are asked to walk in the footsteps of Jesus, and it seems that has a far more figurative meaning than literal.  I'm OK with that too.  Still, if some of the old ways were kept, I think that may be key in understanding his role in the Jewish community as a leader/teacher.  Plus, only then will they know Jesus' ancestor's true suffering during Passover: being forced to eat matzah and gefilte fish for a week.

Happy Passover and Happy Easter (and for those who don't celebrate, happy weekend!).