I'm so sorry your dad is having trouble. I went through the same thing after my ileostomy surgery. It took 10 days for it to start working, so I had an NG tube in and was vomiting a lot. Tell him to hang in there, because once it starts working, he is going to feel soooo much better! And, it will start working soon. Sometimes surgeons don't tell you that it can take up to 2 weeks for the stoma to work and how miserable you will feel until it does.
As soon as he gets output from the ileostomy, they will clamp off the NG tube and take it out after 4-8 hours without vomiting. Then, they will allow him to have liquids (broth), then full liquids (cream soups), and then a regular diet. If he tolerates food without throwing up and his ileostomy keeps working, then he can go home. It all happens very quickly once the ostomy starts working.
One thing that really helps is for him to walk the halls as much as possible. Walking helps wake up the bowels, so they'll start working faster. I hope he gets relief soon!
Dx'd Crohn's in '99 at 28. Proctocolectomy and ileostomy in '06.
Disease-free, medicine-free, and very thankful to be healthy again.