This is going to overlap a bit with ThunderBow....

This dream feels like the overlap of half-forgotten memories, and a reflection of who you were and who you are becoming...

First - were the adult you and the kid you separate, or was it the same you, but you were simply different ages at different points in the dream? (More simply put, was the adult you able to interact with the kid you?)
-->If the two are separate characters, this is most likely a subconscious reflection on how you've changed. More on that shortly...
-->If the two are the same character, then this is a change of perspective. It could be a subconscious regression, or it could just be your subconscious trying to come to terms with something unresolved in the past.

The depression here is an emotional theme. I wonder how your emotions were when you went to bed?

There's a big theme here about expectations. Let's dabble on that for the moment...
I see autism on your primary concerns list. One question you may want to ask yourself (and this will come back up later) is "How am I seeing what is expected of me in the world? Is it having a negative effect on my mood and outlook?"

The first major point in the dream is the statement of "why don't you do something for your brother?" Did you grow up feeling that you were being put second to your brother's needs? Does it seem true now, reflecting on it?

The dream flashes forward to you as an adult...briefly...and how your mother steps in in time to save you. This is most likely a reflection of how the first perspective has affected your development and growth. Do you place too many expectations on yourself? How do you see your part in society?

Your mother saves you. This is important. Since everyone in your dream is you at some level, the question becomes - What of your mother's traits do you see in yourself? Which of these have been helpful to you? What about negative traits? (I'd be willing to put money on the fact that if you felt like you were being treated lesser than your brother, you saw it from your mother...I'd also be willing to bet that the expectations of you needing to do things for him translated into giving to others without taking care of yourself...) Remember when I said how you see what's expected of you will come back? Here it is.

-->Of the expectations you might be feeling weighed down by, which are from others and which are from yourself?
--> Now, which of these are realistic and which aren't possible to meet?
--> Which ones are you feeling most hurt by not meeting? Is this helpful? Is it realistic?

From the being saved you return to your young self being abused for being selfish. As a child how did you handle the expectations put upon you? Is the abuse relevant to some hardship from your past?

Addressing the young you after the dream is a nice starting point. I'd encourage you to also look to that part of you that relates to your mother, for strength. And then taking a hard look at what is, and what isn't selfish...and what expectations you have on your plate. Of those, embrace the ones you've succeeded at, and cast aside the ones that are unrealistic. The only ones you need to concern yourself with are those that are feasible and helpful.