Should I euthanize my dog to stop his suffering?

[Ewad7]

My 13 years old pomeranian has been diagnosed with kidney failure about 2 months ago. He also has diabetes for the last 3 years. I thought I got the hang of his kidney to make him feel comfortable, yet he developed very bad skin infection on his entire body, worst in groin area and back legs to the point where he would not want to walk much. The vet tried 4 different antibiotics ( amoxicillin, then rilexine then Zeniquin and last doxycycline) and none have cleared the infection. After the doxycycline in liquid form my dog has been vomiting constantly. He can’t seem to swallow comfortably anymore. Even water seems to be a problem. His breath is very acidic. I tried to give him food through the syringe but he vomits everything, even after water. I gave him subq to keep him hydrated.
There are two vets at the clinic, I spoke to one few days ago and he one said that If doxycycline doesn’t help I should think about letting my baby go, since the infection could be kidney related, not bacterial related. They took a sample of my dogs hair to test it and it came out that he has one bacteria present, which I can’t even pronounce. Yet, the other day when I called and spoke to another vet at the same clinic ( who knows my dog situation very well too) to tell her symptoms my dog is having after doxycycline, she said to come get another antibiotic..... I want to ask for your opinion.... do you think I should stop, not try another anytbiotic because of the symptoms... he can’t hold water... or should I listen to the vet and give him new antibiotic, eventhough he hasn’t eaten the last day or drink much.
Thank you for all your help in advance.