I'm not 16, but I have a friend who's about 3-4 years older than me. She constantly tells me how the phrase 'sweet sixteen' is just a sugar-coated lie to make teens feel happy about growing up. With that, I'd like to say that I'm sorry you've actually gone through this. All this wasn't your fault, and the fact that your boyfriend actually cares about you is sweet. But please always remember that you're loved and are important to them. From a bystander's view, I can just say that your brother was in the wrong for even starting that fight on your special day, as well as your mother who didn't even bother to apologise.
It's honestly crazy that some people even forget about joyou occasssions like these anyway.

Happy birthday, by the way. This was just purely unacceptable of your family, so i hope that whatever else u wish for today will come true in the near future.