I think your interpretation is a little off there. The Euro has weakened every time there was news about the crisis getting worse. Only when there was some sort of intervention that essentially kicked the can down the road did the Euro increase again. And it has only been increasing against other very bad currencies like Sterling and US$ in an ugly contest. Against currencies like the CHF, AUS and especially gold the Euro has been decreasing significantly.
I agree that forcing Greece into default would be very positive for the Euro, but the exact opposite is what is actually happening. It's like an alcoholic sitting at a bar saying "I'm serious bar man, I'm giving up drink tomorrow, and to prove it to you I will not have the whiskey chaser with my pints tonight."
While the ECB may not be printing money at the same level as the BoE or FED, they are still printing money. More importantly they are way ahead of other central banks in qualitative easing. It used to be the case that only investment grade bonds could be deposited with the ECB as collateral for loans. When Greece slipped into junk bond territory their bonds were first temporarily accepted and now Greece's bonds will be accepted no matter how bad their rating becomes.
The reason people are buying German Euro bonds has not so much to do with confidence in the Euro, but with confidence in the German economy and the fact that if the Euro failed the Deutsche Mark would once again be seen as one of the go to currencies.
I agree with your arguments that led to this conclusion. I think that leaving the Euro would be pretty much impossible at present unless there is a significant default on debt.
This is true, but remember that the Euro had nothing to do with providing that stability. If anything, you can argue that the EMU has made conflict, at least verbal and political, more likely.
The founders of EU project had specifically in mind to provide an environment in which war in Europe would not occur again. Their ideas were based on something French economist Bastiat said "If goods don’t cross borders, armies will". Thus the idea of free movement of people, goods, services and capital was born, and its success in fostering peace and incredible economic cooperation was immense.