I just took my dog to the vet because he was breathing heavily, wheezing, coughing and not eating.
It turns out that he has a none-cancerous tumor on his heart that is beginning to crush his wind pipe. There's nothing we can do about it. We have him on pills to help open up his bronchial tubes, but he won't eat. The vet says because he is more concerned with breathing than eating. If he doesn't start eating he'll die.

How can I get him to eat? What can I get him to eat? I need help...

If he did not have this medical issue I would give different info (no dog ever willingly starves to death) BUT I think you need to do whatever it takes to get him to eat. Boiled chicken, something else. At this point you need (and you know this) to keep him well nourished. Does he drink? Is solid food a problem? Maybe some type of soft food (even a puree) would be a good idea.

I'm so sorry you (and he) are going through this. You obviously care very much for him and it must be painful for you to watch him struggle to breathe.

I too am very sorry you have to go through this, it is horrible to see a loved one in discomfort.

If it is so bad that all his energy is just going into breathing then it think it might be time to think about making some hard decisions. You don't always have to watch them suffer, sometimes ending things early is the kindest gift you can give.

If his breathing is not as bad as it sounded in your post then I would be trying some very soft food.
Puréed food that he can more drink than eat and will go down his throat much easier than solids.
If you own a blender that would be ideal, you can add some chicken or even canned dog food with a little puppy milk, whizz it up and try that. If you don't have a blender try soaking some dry food until it is very soft in some chicken stock, you can try adding his favourite treat to it as well but I think the most important thing would be to make sure it's soft.

I am also very sorry to be reading this. I know how hard it is to watch your family members suffer. If the circumstances were different I too would offer much different advice. But at this point if you can get him to eat anything I would give it to him. Whether it's hot dogs, rice , burger, or baby food. Has the vet suggested him being put in an IV? I know it's usually just for fluid intake, but any bit of nourishment at this point is going to help.

I am assuming that the tumor on the valve is un-operable?