Sorry to read this. Have you discussed it with the Vet? Only way I know of to bypass the stomach is to have a feeding tube inserted.
I had a Sheltie years ago that had an esophagus burn and he was on medication to keep it coated but I can't remember the name and his records are packed away. It did help and he could eat a soft diet. Sorry, but if it is stomach cancer, that is painful. Did your Vet give you any meds for nausea and reflux? You might check on a liquid diet for dogs (like Ensure for people). You could get a dental syringe ( they have a curved end) and that can be put way back in the side of the mouth and liquid be given in small amounts at a time. Have you tried blending a gruel for feeding? You could use bland ingredients like cooked chicken and rice and some vegetables. I would add some calf liver.
If worried. Your Vet should be open tomorrow and maybe you can ask these questions.
Good luck.
Thank you so much for your reply :) Yes - have seen vet, done x-rays, due for ultrasound this Thursday. I feel it's too late, so taking steps on my own. The more I read, the more I think it is simply a pretty bad case of gastroesophageal reflux. This morning I gave him some Carafate, along with a mix of soaked chia seed and honey. This "food" mixture went right dow - he didn't choke, gag, or try to spit it up :) I not have an optimistic outlook that overcoming the acid reflux is possible. He's only 10 - and seems to have a great deal of energy despite not eating. No blood come out either end ;) - so I'm ruling out stomach cancer - though the vet expressed concerns about his thickened stomach wall. 'm hoping a few days of chia seed and honey will provide a perfect environment for his esophagus to heal to the oint that he will accept other foods.