So sorry to hear this, but your brother already knew you loved him, as your actions during this showed, so your actions before this surely showed him as well. Do not punish yourself for not getting there in time, for he had you there with him already, and you were holding him tight to your heart the whole time. I'm just so glad you didn't have an accident driving! It's gonna be a tough time ahead, so please take care of yourself!
I agree with Daniel 100% on this. I was going to say that you did better than tell him you love him. By way of what you did and what you went through to get there, you more than showed him not only that you love him but how much. You can be sure that he got updates on your progress. The nap was a smart thing to do. Without it, your family may well have been mourning the loss of two brothers. Very sorry for your loss.