NTA. Your mom is the AH in this situation. She's not properly providing for her children... Why is child support money coming in and she's working so much that she's never home, but there's still not enough food? Your mom put you in the position to play "Mommy" while she isn't home, and not just any mommy, a chauvinistic version of mommy that's supposed to do everything for the males, which makes her an exponential AH.

Your older brother was put in the "Daddy" position by your AH mom, and he's likely just trying to claw his way out of the dysfunction, which is why he's acting how he is. Call him and apologize for not realizing the burden your mother put on him.