Is GME common in Yorkshire Terriers? Sorry if it is a dumb question, but better to reach enlightenment then not at all right...
OP:
You always have the right to do as you please but the major concern, as I am sure you know, is Polo and his health. Whether or not we agree with your treatment, the best and most mind easing solution is to go ahead and get the MRI. I am sure after already spending so much money they will see that the love you have for Polo is never ending and genuine and willing to set up a payment plan of some sort.
I would be willing to donate to the vet office on Polo's behalf!
God knows your heart, no one here does so we can't judge you without committing a sin ourselves.
GOD BLESS YOU AND POLO!
AND I AM VERY HAPPY AND TICKLED HE IS SHOWING SIGNS OF IMPROVEMENTS!