I solved my WP problems.
The permalink problem was because of a missing .htaccess file. I created one with write permissions for WP, and changed the permalimk setting back.
The white-on-white issue was solved by setting CONCATENATE_SCRIPTS to false in wp–config, so it seems to be a caching problem somewhere. Later I will take some time to switch back and flush some caches (at least where I have the rights to do it).