Hello again Rina,
Jewish ancestry is probably very difficult to trace and your ancestors seem
to have moved a lot.
There's a very knowledgable German historian who has specialised in the
Memel area: Ruth Kibelka/Leiserowitz.
I think her husband is Jewish. She has a webpage with some information on
Jews in East-Prussia where she
invites visitors' inquiries and commentaries:
http://www.leiserowitz.de/Juden/englishindex.html
Regards
Lutz Szemkus