You're going the most expensive time of the year, and 2014 may be another expensive year for Summer travel. If you begin your trip 6/2 or 6/4, you may save a little. Of course Monday, Tuesday and Wednesday departures are usually the least expensive days to fly out. We travel in the Spring as it's cooler, less crowded and cheaper.
By all means, go open jaw into Paris and out of Munich or whatever city you'll be close to. With 4 weeks, you can really cover some territory and not even be hurried.
You can fly SFO into Paris nonstop on Air France. Unfortunately, Paris to Munich is not a big route for budget air carriers, and flying between the cities may be expensive.
I too watch ITA Matrix closely, and it just takes a few seconds to sign in and check on airfares. I've found Fareboom.com to be absolutely the cheapest place to purchase flights, and they will send you an email whenever a fare is reduced.
We're flying into Budapest and home from Prague the end of March. I spotted a one day sale on ClarkHoward.com out of selected large cities for $728. Fares had been running $1050ish for quite sometime. Airfares dropped to $850ish last week, but they're back to $1000ish this week.
You have plenty of time to wait for a better airfare than $1,600. Airlines are expected to feel out demand after the first of the year, and I wouldn't be surprised to see more one day sales. Just get a base line price for when you're wanting to go, and be ready to jump on a deal when they appear.