Breastfeeding my new born baby with hypotonia

Patient: 8 Days ago we had our first baby (2,8kg and 50cm). He was diagnosed with severe Hypotonia and admitted to NICU. He has gained strength in his legs, but his upper body and neck remains very floppy. He is struggling to feed and has an NG tube. He can drink small amounts and has finished a bottle once. Please could you advise me on the best breastfeeding supplements (I am extracting) to assist with his energy levels, as well as any other techniques we can use to assist him to gain strength while in ICU

Symptoms: Hypotonia, Floppy baby