Jesus was a "Jew" because he was of the lineage of the tribe of Judah which is 1 definition of a Jew. He did not practice religious Judaism. He practiced Torah Law which by that time was only a shred and today is rendered moot. He dismissed Judaism as "customs and traditions which make the written word of God to no effect".
The fact that Christians do not understand Judaism, as well as most Jews for that fact, works to your detriment. Modern day Judaism is based on the "oral law" which was not rendered by Moses or God. It is a cult.