The date for Easter was commanded by Constantine the Pontiff I'm not sure how the date for Pasqua was arrived atsorry; There is only one Passover and is is when YHvH commanded it.
b'SHEM Yah'shua
of the Roman church in 325 AD at his council of Nicea.
but it is not from the Holy Word of Elohim.
If you want to be Jewish I am sure any Rabbi would gladly give you instructions in the faith. They welcome converts and you would be treated with all affection and respect.
Constantine was never a pontiff in the Church. Orthodox and Catholics were united at the time so you might also query Orthodox on this matter.
You will notice in reading Scripture that Sts Peter and Paul both were very clear about Christians still not being bound by the Torah. It did take Peter longer to get it but I guess visions from God will finally get the point across.
One cannot be a Jew and a Christian at the same time. If this was the case than Christianity would never have expanded beyond Israel and it would have remained a small Jewish sect. With Jesus being regarded as no more than a very wise Rabbi.
But you can not believe in the Risen Christ and remain a Jew. To try and do so is both an insult to Judaism and Christianity.