The Star of David is a well-known symbol of Judaism. To wear or use one when one isn’t Jewish or isn’t in the active process of officially becoming Jewish is cultural appropriation. I’ve written in the past about this exact topic: Ask A Jew: Wearing the Star of David.
At a Jewish wedding, typically at the end of the ceremony (although the timing varies in different communities), the groom stomps on a glass, the glass breaks, and everyone shouts, “Mazel tov.”
During Pesach (Passover), there are restrictions on grain (wheat, barley, spelt, oats, and rye), yeast, fermentation, and any items that have previously come in contact with those.