Shelley's right - if Teddy's sat is at 90, that's pretty dang good! I don't think I would keep him on the oxygen line with a number like that. If you can do the ABG, that would be your best bet, if not, I think I'd seriously think about bringing him home so he's in a familiar place with his family. He's not going to be getting a lot of oxygen from a line, it's just not an efficient way to get oxygen into an animal.
I like the barking idea. Izzy hardly ever barks anyway, so getting her to bark is like getting a rock to dance, but if Teddy's a barker it's definitely worth a shot.
I know it's heartwrenching to see, but my vet made me feel a lot better one time when he said that even with the labored breathing and the fever that she wasn't suffering. She wasn't comfortable by any means, but she wasn't suffering. If you've ever had pneumonia where it's hard to catch your breath, know that the feeling is very similar. It sucks, but you can make it through it. This stuff is horrible, but these dogs are stronger than any human will ever be. Their capacity to deal with illness is staggering. And don't forget -- pink and panting, you're fine, even though it's tough. Blue and heaving for air, you're in trouble.
Get some rest for you, and I guarantee things will look better. I would hate for you to make a quick decision while you're exhausted and then regret it. Get some sleep and really think about what your heart is telling you. Only you know what's right. No one will ever judge you here, no matter the decision you decide to make.
Hang in there, and call me if you need me.