I get mixed signals big time when I read your email. You are very attached to your mom, and even though you want the adventure of a new place, you don't want to lose your closeness to your mom. I also hear that you enjoy the way people look up to you, and come to you for assistance, and that you know that won't be the case in Texas - at least not for awhile while you're beginning to get to know people.
I think if you really want to go, and that's what's right for your family, then you should take the risk. You can always move back - people do - if it turns out to be the wrong move.
Be realistic though. Be prepared for things to be different and lonely for a few years. If you prepare for it, you won't be surprised or disappointed by it. And do things that will keep you connected to your friends and family back home.
I moved lock, stock and barrel three years ago. Here's my advice. First, keep your old cell phone number so your friends and family can easily find you. It is very difficult finding new friends, in a new place, no matter how outgoing you are. People have their lives mostly settled, and it will take you some time to find folks who are willing to "let you in" to their circles. We joined a synagogue, and we attempted to make friends with families whose kids were in our kids' classes, or on their ball teams, etc, but it's been slow. After three years, I can say we now have a handful of families we can get together with either as families or couples, and I have only a couple of "true" friends. I actually got involved on Mamasource as a way of having "girlfriends" to chat with. It's not the same, but it does help.
As for your mom not traveling - I'd strongly suggest that you start a travel fund for yourselves, and religiously plop money into it every month - whatever amount is comfortable for you. That way, when you want to go see your mom, you'll have the funds. You might also consider getting a Southwest Airlines (or other) Visa card so that every purchase you make goes toward a free ticket. The $$s add up fast, and you can get two or three tickets a year ($16K = one ticket on southwest). I do that, and I put every single purchase on my card. I do NOT carry a debt though - I still live within my means and pay my card off every single month - so you have to know yourself and whether that's a safe thing for you to do.
As for your brother taking advantage of your mom - I'm not sure how he does that, but it may be that the two of them have to work this through by themselves. You may not be able to stop it from a distance. You may have to let go. You may have to remember that serenity prayer (God grant me the serenity to accept the things i cannot change, the courage to change the things I can, and the wisdom to know the difference!).
Good luck to you!