Have you been to the Netherlands?
Hi, I saw Your new route and I think You will miss pretty much. I can give You some tips from Muritz (Germany) and through Island Usedom. But later, now I'm going to work.
In Kluki there is a nice museum, here is a photo gallery from that place: http://muzeumkluki.pl/galeria.html From Łeba it is close to Slowinski National ParkDuring summer holidays in Łeba, Jastrzębia Góra, Władysławowo and all Hel Peninsula there are a lot of people. It is popular destination for summer. Let me know, when you will be in Gdansk. Maybe I'll have time to show you around or cycle one or two days with you. Instead of cycling through Russia, you can go through eastern Poland directly to Lithuania.