Please help me save my dog’s life.

We have a 3 year old Boxer, who was full of life and love and energy, up until a couple months ago.  He needs surgery on his esophogus as he is not able to eat or drink enough as he cant swallow properly.  We spent all we could to figure this out, but now cannot afford the cost of the surgery.  I have tried everything I can think of to help him - dry food soaked in water, wet food,pureed food, meatballs, tiny cut up pieces, hand feeding him, smaller more frequent meals, trying to keep him vertical when eating, watermelon for hydration, I've made him "jello" pieces that are beef broth and gelatin for hydration.  Nothing is helping him and he is wasting away.  What was once a strong, proud dog is withering away.  I volunteer with a dog rescue, and he looks worse than some of the newly rescued dogs.  I keep his jacket on him because it is so cold out right now, and also because it makes me tear up to see how skinny he is.  I can barely look at his big brown eyes.  We have a 2nd dog, who is a rescue, that only came out of her shell because of him, and she adores him.  My stepdaughter is also going to be devastated if we cant help him.  If he was older, I would accept he had had a good, long life, but he is still so young, and such a sweet dog that everyone loves.  I am so upset with myself for not getting him pet insurance.