Hang in there Tufty, you're doing great. We can't ever predict who will be supportive and who will act differently after we quit. You can only control you and again, you're doing great. Your brother might just not know how to react; although I would do it differently than he has done to you.
Like some of the others have said, maybe it's time to have a talk with your brother about how his actions make you feel. I'm one of those people that if something's bothering me, best to get it out in the open quickly rather than let it fester.