Itn to hate your boyfriend's family?

My boyfriend and I have been together for three years. We've talked about engagement, and I think he has an engagement ring ready to go and is going to ask on our anniversary, which is tomorrow. I love him dearly, but his family.. Not so much. They're constantly rude to me. They're the up-tight, go to church every Sunday, Christian type and well.. I'm not. I'm freaking out because I want to say yes but his family has this on going grudge against me! I'm three years younger than him, his dad has made comments like "are you picking your middle schooler up?" We moved in together a year ago, we get comments like "you're living in sin!" When my boyfriend brought up the subject of a wedding to his dad, his dad's exact words were "you should just go to the courthouse and get married. Having a wedding after living together is very tacky." I shit you not. We moved in together because we're both in college and wanted to save some money. My boyfriend and I adopted a puppy from the shelter, they said to take him back because he would ruin our things! Luckly, his sisters and brother like me. It's mainly just his parents. And his grandma. I posted one of those bad lip reading YouTube videos on Facebook (that I personally think are hilarious) and his grandma literally commented "I didn't laugh at all." Like??? What have I done wrong? I've always took the high road and avoided conflict. I've always turned the other cheek but I'm at my breaking point. I can't handle them any longer! I want to say yes when he asks but I feel like I'll be judged by them! Help! :(