Oy vey. First, there is no such things as “da’as yehudi”. “Jewish knowledge”?! “<i>Das</i> yehudis” is the <i>rule</i> of a Yehudis, i.e. the established way that a Yehudis behaves. As in “vedoseihem shonos mikol om, ve’es dosei hamelech einom osim”. But none of this has to do with “Jewish dress”, or that there is an inyan in preserving it and not dressing like the surrounding culture.
Kisuy harosh for men is discussed in terms of “chukos hagoy”, since the goyim have a religious commandment to go bareheaded in church, and from this comes their insistence that one go bareheaded indoors. (Going bareheaded outdoors was unheard of, both by goyim and yidden, until about 50 years ago, so it just wasn’t an issue; the issue was only indoors.)
The medrash you quoted about names, language, and dress, says that this was their only zechus.