Beautiful story! Only one remark: The Zuiderzee has been called IJsselmeer since 1927. That was the time the Enclosing Dyke was completed. North-East of Amsterdam there is only water, but they could have built a new part of Amsterdam in the future, so that's okay.
I'm sure you're more familiar with the area than I, so I'll just say that on my maps it's still called the Zuiderzee, and I stayed in that apartment watching the boats in 2001, walked the path, and shopped in the area of the cafe. The direction was probably north/northeast, but I didn't think I had to be too exact.