|I can relate to what you are going through. You're not alone!
My Kylie also refused the Nutramigen/Alimentum at first, but only for a couple feedings. I would have done the same as you if she had persisted for days.
If you decide you want to hold off on the testing and do another trial of the Alimentum, I would suggest (based on my experience) that you go with the Alimentum Ready-to-Feed. It's the only formula that doesn't have corn in it (it has tapioca solids instead.) After having our daughter allergy tested we discovered she's allergic to both milk and corn - she was reacting to both ingredients in her formulas. From what I've read, it's not completely uncommon for a sensitive baby to be allergic to both.
Have you tried adding anything to the Alimentum to cut the taste? We tried everything (vanilla, Nestle chocolate syrup, Nestle strawberry powder, rice, applesauce, etc.) but Kylie doesn't really like anything in her milk. But I think most babies will take it better if you add something sweet to help with the taste. I did a couple taste tests myself and I think by far what worked the best (and what I felt most comfortable adding) were the flavoring packets available through Neocate. If you call their customer service and request some samples of the flavoring packets they will send you several to try for free.
We have not had any GI testing done on Kylie. I was never settled with the idea of her having straightforward reflux, even though her symptoms were mostly reflux-type - for many little reasons, but mainly because she did not respond to even high doses of PPI meds.
We had finally scheduled a UGI but I decided to have her allergy tested in the meantime. The tests showed she is an extremely sensitive baby (severely allergic to 22 of the 74 things they tested for), and this finding is more in line with my own instincts regarding her symptoms and behavior.
We are now experimenting with new formula (in the end she couldn't tolerate even the Alimentum so we've moved on to Neocate) and some meds for the environmental allergies. We are also making an appointment to see a physical therapist at the hospital to explore craniosacral therapy, which can be helpful with allergies.
Just some info about our journey in hopes that it may include something useful for yours. Good luck and hope you find your answers very soon!