I am so sorry to hear your yorkie is sick.
I would take him to the vet and take him off of Beneful right away. It is a bad food and could be causing the problem or adding to it.
Have you tried Care Credit? A lot of vets accept and you make payments to the company.
CareCredit® Healthcare Finance - Payment Plans and Financing for Cosmetic Surgery, Dental, Vision, Hearing, Veterinary & Other Medical Procedures
And here is a site with a list of Animal Assistance Programs that may be able to help you:
Animal Assistance Programs
I hope you can figure out what is wrong and that he starts feeling better soon!!