I think this is one of those mysteries that just sort of beautifully works itself out. I had all of those feelings you express, when awaiting the birth of my second child. And, of course, I have a whole new host of worries/wonders now, as I await the birth of my third.
You will be able to make two the center of your world, yes, and at some point, you will actually have time for DP and yourself, too! (for me, I felt that the first three months were spent kind of trying to figure this all out and then, after that, it all felt as manageable as it had ever felt with just one.) Of course, you only have to live each day as it comes and on each day, you'll know how to do what that day requires. That's been my parenting philosophy, anyway, as most of my worries are based in nebulous fears about what is to come, not what's there facing me at any given moment.
There was another thread, I think in the Dec. DDC that addressed this same question and Tara wrote a really great response to it. Tara, do you know where that was or is? It was eloquent and true and (I thought) reassuring.
Just to add one more thought that's probably a bit off topic, one of MY worries at this point in my second pg was that my first would suffer from the attention that was taken from her to be given to the second. In retrospect, I believe that the birth of my second child was one of the best things that has happened to my first. It was good for my first to be relieved of our constant and sometimes interfering attention. Also, of course, some of that attention taken away from my first was made up by the new attention she got from the second, who appeared to love her from the get go. That has been one of the most rewarding parts of this whole journey.