I am sorry to hear you are worried about Bear. My name is Rebecca. I am a veterinarian and will do my best to help.
Were any blood tests, or Xrays done when you took him to the vet?
If you look at his gums, are they pale or white, or are they pink?
If he is anemic, that would cause the labored breathing. The only way to treat anemia is to find out what is causing it. Anemia can be from internal bleeding, cancer, bone marrow disease, or autoimmune disease. The treatment is different depending on the cause.
It will help to know if any blood tests were done. Unfortunately, one cause of anemia in older dogs is a tumor on the spleen that is bleeding.
The thing you can do at home, in addition to the medications your vet sent you, is to keep his diabetes controlled ( how much insulin is he getting? Can you check his blood sugar at home?).
There is a Chinese herb called Yunnan Baiyao that can help with bleeding and anemia, but you probably won't be able to get any today. You can find it online and in stores that carry Chinese herbs.
I am very worried about your description of him, and if his gums are pale or white, he may need medical attention. If you can't get him to a vet today, then get to one as soon as possible tomorrow. Let me know about whether blood tests or Xrays were done; that may help me to learn why he is anemic.