So that means the other party needs to fly to Germany in early May.. Like May 8th or so?

Honestly, I think what's happening is you are waiting too late. Airfares tend to go up not down as you get closer. I think at this point, barring a great sale, you are going to start to see the airfares climb. You are less then 60 days out and in my expereince, that's not prime buying time for Europe.

Make sure you give yourself LOTS of time on some of these creative connections. If you miss the LCC flight from BCN, London or whereever it's going to be costly. Plus if the cruise leaves 5/29 I would arrive in Venice no later then 5/28