I was hoping to hear back from you with some additional information, but I can answer your question now and if you need any further information, just click 'Reply.'
The bleeding your cat is experiencing is of great concern. I'm so glad you had him checked out by the vet and I think the next best step would be having that endoscopy with a camera attached, to get a good look at your cat's stomach and try to find the cause of the bleeding. He could have damage from excess acid being produced by his stomach (like a bleeding ulcer), he could have a cyst or tumor that is bleeding, and there are many other possibilities, so imaging is the next best step.
It's encouraging that he has an appetite and you did the best thing in changing to a wet food.
The occasional blood in his stool can be caused by the same problem; a fecal analysis should be done. If your vet can also take a look at his intestines and colon, you could get a diagnosis and treatment for the problem found. Lymphoma is a common condition in cats' intestines and it is a form of cancer, so having these tests are very important.
I hope all will be well with your furry boy, once the problem is identified and treated!
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