Euros just today are trading at 0.89/USD. That's a huge devaluation already and will be trading at par soon if this continues. As for defaults, that is effectively what happens when a country devalues it's currency (or re-institutes it's currency) and repays expensive money with cheap money. The U.S. Did it in 1971 when Nixon took us off the gold standard. It's a soft default ( a hard default is when they simply don't repay at all).
Yes,
if. That does not mean the Eurozone will implode and the EU will tear itself apart, as you sketch it. Both remain viable even below Dollar parity.
I understand that the European financial and political situation is enormously complex, but I don't need to know all the ins and outs to see that a monetary union with no fiscal (much less political) union is untenable given the very different incentives and motivations of the various players.
Actually, that is exactly what you need to do. You can not understand Europe if you do not understand its organisational complexities. The structure of contemporary Europe is unlike anything before and can not be analysed through 'traditional' models. You will grossly misjudge the situation every time. Even European press does not seem to understand Europe, though that's pretty much a given with journalists anyway. I don't know where you get your news, but I will tell you this: American press on Europe is downright idiotic.
How long will German Taxpayers subsidize the profligacy of the South? If they take a haircut on Greek bonds, what's to stop the other peripheral countries from demanding the same? It's as if a family has a problem child and if they show tough love the kid will rebel and run away, but if they go soft, they other children will rebel also, (correctly) perceiving the preferential treatment as favoritism.
This latest demand for WWII war reparations is just icing on the cake. Hardly any Germans living bear any responsibility for the Nazis. If I was a German, I'd rather burn my money than give it to Greece. Now supposedly they are cozying up to Russia as well so we can ad "disloyal" to "lazy" and "dishonest" as descriptors of Greeks. Germany and the other creditor nations won't cave. They can't or their electorates will (rightly) boot them out of office.
Again: Germany is not alone in this. It is not German taxpayers alone who carry Greece. The 'peripheral countries' are in fact among the least indebted and their economies are growing strong. They are as annoyed by Greece as are the other European countries.
As you said yourself, Syriza's 'demands' and their cuddling with Russia are no more than pointless provocations to make themselves look good to their voters. Their real demands softened up as soon as they got elected.