Complex sentence: Feeling that the name "Chuck the Duke" sounded macho, he wanted to add a Polish sounding last name, as Poles were frequently picked on, therefore he turned "Chuck the Duke" into "Chuck Dukowski".
Split into simpler sentences: Feeling that the name "Chuck the Duke" sounded macho, he wanted to add a Polish sounding last name, as Poles were frequently picked on. He turned "Chuck the Duke" into "Chuck Dukowski".