This is such a heart wrenching story. Our 4 yr old baby Nala had the same symptoms as Jake. She also had blood in her Urine though. We took her to the vet, and she spent 2 nights on IV's and some medications. The vet also started to notice Nala's belly was swollen, so he sent us to a specialist, for more testing. When we dropped her off, we got a call about an hour later saying that they found a hole in her intestine, and the fluid leaking from it was causing her stomach to bloat. She had emergency surgery that night, and made it through. Her first day of recovery was rough, but on the second day, she walked some and actually ate some baby food, and drank some water. Unfortunatly she passed away that night. The toxins in her system from the intestine leaking was what she couldn't fight anymore. 2 days later a liver biopsy came back positive for cancer. The vet thought that she may have had a small tumor on her intestine, which ruptured, causing the hole, but couldn't say for sure that this is what caused the hole.
As I was reading your post, I was debating wether or not to tell you my story. I am new to the board, and really didn't want to scare you, or come off as a jerk, that is being negative. It just concerned me when you said that Jake's stomach looked swollen. Our regular vet didn't detect the hole, but the specialist saw it on the the test that our regular vet took. We are not blaming anyone, but if the hole was detected earlier, that would have been less toxins in Nala's system. She would have then had to fight the cancer though, and I'm not sure if she could have taken that. I know it would have been hard for us to watch her go through it, after a major surgery.
Our thoughts and prayers are with Jake. I hope all turns out well.