Too scared to come out but I have to if I wanna be happy

I knew I was trans like 3 years ago and am out to my parents and friends (and my old classmates and teachers) but my mom still refuses to call me by my preferred name and pronouns unless "I'm out to everyone" meaning I have to come out to my stepdad's side of the family. The thing is, I've overheard them saying transphobic stuff a couple times, that's why I haven't got the courage to come out yet. Also because I don't like making a big deal about stuff or being the centre of attention, and my cousins are still kids and I don't wanna like, confuse them or anything or give them the idea that you can just choose your gender like that and then get blamed if one of them turns out queer or whatever. I just wish I could stop being a coward and just tell them without caring about what will happen. I thought about that multiple times, about just not caring anymore because it's for my happiness and I shouldn't care about what anyone else says about it. Well I was a wimp and I do care because if they react badly I will have to coexist with them a lot and just endure whatever they do. I also think it's bullshit from my mom that she insists on calling me daughter and other feminine language. I generally pass to people who didn't know me as a girl and everyone new I meet just assumed I'm a guy automatically. I like that I pass and when I'm out of the house I feel so much better because of the opportunity to present fully male. I wanna feel happy inside of my home too. Does anyone have any tips on how to stop being a wimp. I really need it.