9 week old, nj tube, projectile vomiting

Hello, my name is Gen and I am posting this for my cousin. Her baby boy is 9 weeks old and weighs 8.5 pounds. At birth he was right around 7 pounds. He spent one week in the hospital nearly 3 weeks ago because he was dehydrated. Here are the things that have been done:

Colonoscopy, showed irritated patches in the colon, nothing else abnormal.
EGD, normal valve openings including pyloric.
Meds: Neocate by NJ tube until he pulled it out a few days ago. Reglan and Prilosec.
Diagnosed with Delayed Empyting.

During this first stretch in the hospital the doctors were clueless. They did the NJ tube as a last resort and it seemed to be working as he was gaining weight with less vomiting. However, since removing the tube he has lost 1 pound. They are planning to do an MRI to make sure he doesn’t have a problem with the correct signals to digest food (seems unlikely to me since he was gaining weight) and he was able to take 5 ml per hour right after the NJ tube removal. When increasing to 1 oz he began vomiting again.

He was sent home from the hospital after being rehydrated again this week and does not see a specialist until Monday regarding the feeding tube that he removed.

I know that I do not have all the info, but my cousin asked me to look into things and the things I am reading for treatment of GERD are not being addressed. I am hoping to find someone that has been through this that could offer some support and some information. The doctors are really considering this little man a mystery and his face just breaks my heart.

Please, if you have advice for questions to be asked, tests to be run, treatments to pursue, let me know! I will do my best to answer questions, but I am praying that this might offer a breakthrough for this little man. Thank you so much in advance!!