I think you should slow down. Have you spent enough time with your boyfriend face-to-face to be really sure that you love the man, not the image he projects online? (Sometimes people are disappointed to find that the “chemistry” isn’t there in person.) Have your parents met your boyfriend? Have they had an opportunity to get to know him and to understand why you love him? Currently, they only know he isn’t of your faith. Maybe spending time with him will help them understand other powerful reasons for your choice that balance out their concerns.
For both reasons, it would be wiser for him to come to your city for the holiday, instead of going off with you to Istanbul. Do the mature thing. Ask everyone to have open minds and bring them all together. If your boyfriend isn’t willing to do that, he’s not the man for you.
It’s just true that we don’t just marry our mate. We also “marry” their family. Marriages that have the support and love of the families involved tend to be stronger and last longer so it’s wise for the two of you to do all you can to make those positive connections.
I wish you well.