I am so sorry things aren't looking good, I would be tempted to change his food to make sure it isn't that, and I hope Caroline will be open with you, I ask my vet what she would do, and at first she was reluctant, but she is now open with me, so if Caroline is a bit reluctant at first, do push for an answer, you need to know all the options to decide if you are being fair or not. It is such an awful place to be in, but I know you will do the best by Boy. Keeping you both in my thoughts.