Because you are inexperienced, I would get it to an avian vet for an examination. There are so many things that can go wrong with handfeeding and it would be better to get a professional opinion. If you are not able to do this, what about seeing if the experienced breeder could look at your bird and assist with the handfeeding?
I am sorry you and the poor bird are going through this and hope you will be able to find some direct assistance.