deepNdirt;
I am not sure that I understand your post about Cushing's. Since it is a common issue in Beagles, I have done a good bit of research on it. Cushing's is too much cortisol (natural steroid) in the body, due to an overproduction by the adrenal glands. It is manageable, and is usually not something that is fatal. What owners usually notice first, is a ravenous appetite, (of course, with Beagles, how can you tell?), and an increase in water consupmtion, therefore more trips needed outside to pee. Yes, the disease can make the dog look unthrifty, and I'm sure being hungry, thirsty and needing to pee all of the time isn't fun, but it isn't fatal.
If Oscar, truly has Cushing's, ask your vet about ways to manage it. There are several different ways, and I expect your vet will know which is best for you and Oscar.
As far as Little Odie; I am always saying that it takes about 6 years for them to actually become the dogs they will be. I am glad that he is your truck buddy! It is never the same as the ones that we lost, but each is endearing in their own way.