This is the most painful thread I've ever followed here at BYC. I had nightmares last night about your situation.
You will be in my thoughts for a long time. I surely agree about trying to treat them, but I would add that if one of YOUR original birds dies of this thing that you have a necropsy done. Some states have that service for not a lot of money, and it might save you from a lot of later worry. It is better to know than not. If they are ill from an unrelated source (not likely, but possible), you need to know what the infection is.
Please let us know what happens long term -- in 2 or 3 weeks at least.
I'm sorry that you are having this terrible situation. It is really sad when you become attached to them and they are sick. I agree that if you lose your roo that you should try to have a necropsy done. That being said, however, even if you treat your flock, it can be lousy to have birds that will continue to be carriers or have an underlying illness. We have our first small flock of 3 hens and 1 of them has had a wheezy respiratory illness that comes and goes for 18 months now. A local vet told me to never bring another bird into my flock until my current girls are all gone, even though none of the others are sick.