If I had a concern about weight gain, I would see nursing to sleep as an association to value and keep. More nursing = more opportunities to take in calories.
25-30 oz is actually a bit on the high side. Kellymom says that intake varies from around 19-30 oz per day. And pumps are generally less effective than babies are at getting milk from the breast. Did the IBCLC suggest that you use a hospital-grade pump?