J.,
I just ordered the book called "The Conteted Little Baby Book" by Gina Ford anmaybe what she would say is that she would like to congratulate you on a great routine that you have established and for your genuine care in your baby's sleeping patterns/habits. However, this might seem like common sense, but it is a start. Here, in Germany, we have curtains AND these blinds that can be put down that makes the room pitch black where you can't see anything. Maybe your baby would sleep better if there was not one trickel of sunlight coming in? I am sure there are alternative methods of not going and installing these slides, but it is an option. Also, Gina Ford does say something about getting rid of that last feed in the night, so you and your baby can get a full nights sleep. I am not that far in the book, yet. And ... every child is different, some need more sleep, others not. If your baby is eating right, growing at the recommend rate, and is a content baby during the day, then, I would have to say that this is o.k. Last but not least, try to get rid of the sleeping in the arms. Maybe the darkened room idea will help and it will take a few days to break the sleeping in the arms habit, but the few days of adjusting and a bit of crying when you put him down will outweigh the benefits in the LONG run!
Hope this helps a bit. I am new at all of this, too!
Sincerely,
N.