I believe Babywise and the Ferber method are similar. I have read Babywise, but not Ferber, but from what I understand from ANY of the methods is that you will have some personal modifications based on your baby's individual needs, etc. For example, my son wanted to eat every 2 hours for most of his first month, then went into a pattern of eating every 2 hours in the morning (with short naps in-between), then he'd sleep for 4 or 5 hours, then eat more often in the evening, etc.
I think the routine of Eat, Activity, Sleep, is more important than the time frames (If I remember, Babywise recommends about 3 hours from the beginning of one feeding to the beginning of the next). While my son didn't follow the "every 3 hour" thing (unless you averaged it -- 2 hours one time, then 4 hours the next, then 5, then 2, then 1...) we did follow the routine, he slept well (eventually -- I'll get to this part later), and he got 8 or 12 full feedings in a day. If you do the math, 8 to 12 feedings in a day ends up being somewhere from 2 to 3 hours between feedings, so the numbers they use in the books aren't absolute. They are averages intended to be used as a guide, not a hard rule.
On sleeping -- a baby CAN learn to go to sleep on their own if you let them. I would guess that if a 9-week old wants to eat again before a nap, he's either awake too long after a feeding, or he is simply using the bottle or nursing as his "sleep prop." It's easy to keep a baby awake too long between feedings. He's sitting around looking cute...if he cries, you pick him up and he's quiet, or you turn on a mobile, or talk to him, etc. and he'll calm down. You may be able to keep him quiet, but he doesn't get any sleep! This also happened with my son. I realized that he was getting "backwards" on the routine, so I did an experiment. I checked the clock when he woke up, let him eat, then played with him, talked to him, whatever for about 30-45 min, then I put an apparently wide awake baby in his crib for a nap. He looked at his ocean wonders aquarium and whimpered for a minute or two, then went to sleep. It was soooo much easier than when I waited too long and he was literally so tired that he was too fussy to get to sleep peacefully.
It's hard for us adults to grasp it (or remember from one child to the next), especially if you have toddlers or older children around who can stay awake all morning, but a newborn (meaning a baby under 3 months old) really shouldn't stay awake more than about an hour or so at a time. There might be one interval during the day where a 2 month old will stay up for a couple hours, but that should be the exception rather than the norm. So, if you consider that a feeding takes about 30 min once you count the diaper change, eating, burping...you're left with about 30 min to an hour of activity time before it's time for another nap (which should last about an hour and a half to 2 hours). If you add all that up (yes, more math!) you've got a 30 min feeding, plus 30 min to an hour of awake time, plus a 1.5 to 2-hour nap, when the baby wakes up again it's been about 3 hours between feedings.
If he's NOT up too long after a feeding and still acts like he wants to nurse or have a bottle before a nap, he's likely doing this for the comfort of the sucking action. I'd offer a pacifier.
All of that said, it's really good for you to know that babies really don't have a good routine about anything until around 12 weeks. They're growing so fast those first 3 months that with every half pound or so they gain, they become a different baby. You might find some things falling into place around 8 weeks, but be prepared for it to all change by 10 weeks!
Also, if you make any changes to routine, you really need to give it 3 or 4 days to take effect. Young babies are amazingly adaptable. What will take just 3 days to change now, would take 3 weeks to change in a toddler! That's why I always recommend to my new mom friends to make good habits and break bad ones early, before the baby is old enough to know the difference. Put them in their own beds before they're 3 months, start brushing their teeth at 6 months, break the "nursing to sleep" habit early, etc. The sleep habits were a big deal for us with our first one because I knew I'd be going back to work and leaving her with someone who had 3 other kids to deal with. It would be unfair to my child and my sitter if I had programmed her to need feeding or rocking in order to fall asleep. When there's multiple children involved, there's no way one mommy has time to go through a big song and dance at nap time! If all she needed was a pacifier and a stuffed animal, life would be easier for everyone involved!
Congrats on the new baby! And take a box of tissue and some baby pictures to your desk on that first day back in the office....