I would try going neocate only but carry on expressing so you can go back to bf if the neocate only diet does not work. You could also go on an elimination diet whilst having your lo on neocate that way if her symptoms clear on neocate you will have a baseline and can then trial bf again and see if the symptoms return. These are only my opinions and you have to go with what you feel is best for your dd.
On the allergy test front most medical profesional will not test at such a young age. It is not the first time that I have heard they have been told similar things to you.
