Yes,  this prolonged and refractory hypoglycemia is not BF management!!!!!
this baby probably has something endocrine that is causing the problem:
as the endocrinologist would be thinking of
1. GH deficiency, or panhypopituitarism
2. Metabolic problem such as glycogen storage disease type I,
galactosemia, .....
3. Aminoacid metabolism defect: Maple syrup urine disease, Methylmalonic
acidemia, tyrosinemia, propionic acidemia.
4. Hyperinsulinism:  Beckwith-Wiedeman syndrome (big tongue, gigantism
and exophtalmos),  Islet cell pathology.
5.  Other: congenital heart disease, medications given to mother, birth
asphyxia, hypothyroidism,.....

Since this is not my specialty, will not comment on work up.  Are you
working with a pediatric endocrinologist,  There are critical blood test
to obtain when baby hypoglycemic and adult endocrine would not know.

Good luck

Maryelle