I would give the antibiotics, stool softners, diet and immune supression meds a little more time before surgery. I hope the vets can help with a better treatment plan but ultimately the decsion is yours.

I know it is harder with younger dogs vs older ones. You question yourself if there was anything else you could do. I did that with my first setter when he got lymphoma at 9 years old. My last dog I put down was my first hunting dog that lived 17 years. For christmas this year my wife made a shotgun shell filled with his ashes that I can hang on my lanyard so he is always with me.

Sucks all the way around and it says a lot about the character of the men here.