EUR might drop below USD

No one can throw out Greece from the € zone.
At most they could prevent the central Bank of Greece to have any say on the ECB board.
But no one can prevent the Greece and the greeks from using € inside Greece.

The problem is, the greeks have already moved their money from banks in Greece to accounts in other places like Germany, safe from forced conversion.
Without the ECB giving Greece printed notes and fresh cash, the banks would run out of cash and would have an empty balance pretty fast.

If the Tsipras government stop paying the debts and no agreement is reached with the debtors, it is probable the banks (the Greece's banks first of all) will be the first victims. They have bought a lot of the government's bonds and a lot is in the balance of the Greece Central Bank. So, if the government stop paying, many banks in Greece will be unable to survive and literaly all their accounts will be wiped out (like in Cyprus).

The problem is, then, for other governments in the EU. They are on the hook for a lot of money. Italy, for example, is on the hook for 40 billions (at least, maybe more) if Greece stop paying. This is around 650 €/inhabitants (newborns included). This would go to increase the already large government debt of Italy. It would not be pretty for France or Germany too. They are less indebted than Italy, but not so far back. Italy account for all its government debts where Germany accounts just for a part (some is unaccounted and ont he balance sheet of other entities, but the German government is the one responsable to pay these bills).

Many banks in the Euro Area (and outside) will have their balance sheets devastated and some will not survive. Surely credit will dry even more than now.

All of this is driving a bubble in Germany and some other countries some people see as "safe heavens". People moving their savings from the periphery of the EU to the center make, for a time, the center appear more prosperous and solid than it is in reality. The low interest rate there is fueling a real estate bubble and damaging the return of retirement funds. This is the reason deflation is good and needed, the prices need to fall to compensate for the low/sero interest rates.

In the end, Germany is a lot more healthy than Greece because it reformed its economy fitteen years ago and it was not pretty at the time. Greece didn't, Italy tried and failed miserably, France was trying to play "buddy" with Germany and Germany allowed them to think politics trump economics. But northern economies can not play with money printing and bad loans without risking a lot. It is cold there, like in Finland. And if you destroy your economy because of high taxes and bad loans to profligate spenders when winter come you have no money to heat your home and buy your food.