in bushwick_fonts_url(), family and subset should be urlencoded, as done for example in Twentythirteen and Twentyfourteen.
While this is not an issue on the frontend, it is in the admin, where commas in "tinyMCEPreInit" matter.
In short, just the first font weight will be imported and the following ones will be considered as additional stylesheets to import, giving a 404 each one:
GET mysite/wp-admin/latin-ext 404 (Not Found)
GET mysite/wp-admin/700 404 (Not Found)
GET mysite/wp-admin/900&subset=latin 404 (Not Found)
GET mysite/wp-admin/700italic 404 (Not Found)
GET mysite/wp-admin/400italic 404 (Not Found)