In simple terms, you cant. Only they can.

I can only hope that your happiness will one day become more important to them than religion. Its ignorant (apologies) and people like that hit the news every day. Such a shame - religion was not meant to be abused this way.

Until then your only choice is to lead your life the best you can, and do everything to make you & your new exciting life as good as possible. If that means backing off from your family (esp taking no more calls from your sister until she calms down or swapping numbers if the texts continue), then so be it. Its really really tough, I know (I do not see any of my family now), but at least your partner has come up with the idea of always leaving the door open to them - just make sure its on your terms - ie no more abuse. And no, you're not being selfish - everyone deserves a chance at happiness and you're just going for yours.

I wish you all the very best, and I hope you'll be happy with or without them. You'll have a new family soon of your own.