I'm so sorry that you and P are going through this. You are wise to check the quality of life guidelines because that's the best way to decide when it's time to let go. From t he way you have described P, I agree with you that his quality of life is not that bad at this point. I agree with you that it is too early to bring him in for euthanasia. You see him every day and are the best judge of when he is suffering and his life quality is no longer good. Things to watch for are difficulty breathing, severe fluid retention, appetite loss, fainting or collapse, and disinterest in life.
Your vet has given you the proper heart medications. The Vetmedin, in particular, often gives excellent results. Since the vet recommended increasing it, I believe it would be a good idea to do that. Doing that may be enough to gain a few more good weeks or months for P.
There’s a Yahoo group you may be interested in. It’s for owners of dogs with heart disease, who offer each other support and share information on treatment. You may eb able to find others whose dogs are having similar problems. You can read about it and/or join here:http://pets.groups.yahoo.com/group/caninehearthealth/
There are some supplements that have been found to help some dogs with congestive heart failure/enlarged hearts. They do work best if started early in the course of the illness. If you'd like more information on them, let me know and I'll provide it (There's no additional charge.)
As for the terbutaline, only you can make that decision. Since it doesn't do anything for P's heart, you may decide the potential side effects outweigh the benefits. If the main problem with his trachea is that his enlarged heart is pressing on it, the terbutaline may not help much.
I'm not sure if you wanted anything else, since you said you needed a listening ear. It seems to me you mostly wanted input on whether it w as too early to enjoy him for a few days, and then 'bring him in.' I agree with you that as long as P is getting enjoyment out of life, it is too early. If you need anything else or have more questions, let me know by clicking on REPLY. I hope it will turn out that your vet is wrong about P.