This baby has regained its birthweight, if it even lost any weight in the first place, plus an extra 14 ounces.  What is mom worrying about?  You say she is supplementing after putting the infant to breast -- how much formula is the baby getting?  You do not mention how often she is feeding the infant, nor do you say if she is limiting the baby to 15 minutes each side, or that is all he will take.

First I would make sure she is putting the baby to breast at least every 2-3 hours.  Then I  would suggest letting nurse longer on each side -- or even do the 15 minutes each side, then do it again.  This makes it like two feedings, therefore two stimulations of the breast.  Or pump after the feedings, and supplement first with the extra milk, before giving formula.
(In here I would watch a nursing to make sure that baby is nursing correctly; and also to be sure that he isn't quitting at 15 minutes because he is too tired to eat more due either to not effecting a good latch, or being in a posture that makes him too tired to eat longer (like with the weight of mom's breast on his chin.)

I would also have her start one or two of the herbal galactagogues, like fennugreek,  if she is willing, to see if she notices an increased supply.  Also look at her diet to make sure it is not full of an herb that is a milk-reducer.

Regarding the retained placental fragments, she would still be having excessive blood loss, I think, from a uterus that cannot properly close down.  Or an infection.  But maybe not.

I agree with getting rid of the pacifier and feeding the baby at breast instead.  This will certainly result in more stimulation of the breasts, and hopefully more milk.  If the baby is pacifying himself with the pacifier, when he is actually hungry, he certainly needs to be at the breast more -- though with that weight gain, who knows?

Sincerely,  Chanita, San Francisco