I hope when you say baby is correctly at breast, you are saying so because you have seen it there.  Not just because mom says so.  Too frequently this is the first problem, mom's perception, even if she is knowledgeable, is not accurate when it comes to the very subjective situation.

Equally important to the above:  LOSE THE BOTTLE!!  Use a cup or syringe or your fingers or whatever... 

To help the baby get re-acquainted with mom's breasts, in a non-
threatening fashion, I suggest a   "honeymoon" -- mom and baby back to 
bed and wearing a sling when not, belly to belly, with breasts available 
constantly, so that baby is constantly reminded of their presence,  
and getting accustomed to their feel not related to feeding,  Baby may, sooner or later, reflexively start rooting, licking and suckling when neither he nor mom is paying so much attention.  (I have seen several babies latch for the first time like that, both younger and older than your situation).

During this period of time, a long bath together, or several, letting baby perhaps re-do his crawl to the breast,  may help the baby re-orient to mom's breast.

Until BF becomes established, if baby gets very hungry, frustrated and 
mad, and therefore very uncooperative at breast, I would suggest giving   
 some EBM in a cup or syringe, to calm him,  before bringing him to 
the breast.   And then again, cup or other-than-bottle-feed after to make 
sure he has gotten enough.  I would work to avoid his getting to that state, 
however, by watching him very closely for feeding cues, and responding 
with alacrity to them.

There are a number of mechanical methods that could work to re-orient the baby to the breast.  Since he has certainly developed a strong preference for the bottle nipple, and the kind of flow that comes with it,  maybe a transitory stage is necessary for him to become re-interested in the breast -- for instance, mom could use a nipple shield, to make her breast more like the bottle (I can't believe I'm saying that).  Then when baby starts taking that predictably, slip away the shield.  Also using an SNS might help the baby adjust to the flow differences. 

 In the meantime, and in either case, baby will be forgetting how to drink 
from a bottle, and learning food and contentment come from the breast, 
even if mom has to supplement with ABM.

Last but not least, though it may seem totally unconnected, the baby may 
well benefit from a session or more of body work with either a cranio-sacral
 therapist, or a chiropractor familiar with baby techniques.

Regarding the issue of quantity:  If you have been following the recent 
thread in Lactnet, literature and opinions seem to support the thought that 
breastfed or EBM-fed babies  often do not need or want the volume that 
bottlefed babies take.  So, especially if baby is emptying mom's breast, 
she needn't feel so concerned about the actual volume produced.

I am a little concerned about the fact that pumping does not seem to empty
 mom's breasts.  Also, if this is true, baby might not be getting to the fat, 
and that might be why he  seems to need/crave more in volume than she 
is producing. 

 Also, it means that that mom may be at risk for developing plugged ducts
 or mastitis.  I would make sure mom is preparing her breasts adequately
 before pumping, either hot towel compresses, or showers, or soaking her 
breasts in a tub (depending on their size and shape), and massaging them 
first.  Then also doing massage and compression after the pumping to 
make sure all the milk is out.

When mom decides to wean, either now (I hope not), or when she goes 
back to work (maybe by December you will have been able to explore ways 
for her to pump or adjust baby's feeding schedule), she can ease the 
discomfort of overfull breasts with motrin (for the pain) and cabbage leaves 
in her bra (for both pain and to reduce the engorgement).

Have I covered everything?  I hope any of this is of assistance to you.  It certainly has helped me organize my thoughts.

Sincerely,  Chanita, San Francisco