1) the ability to disable auto set for day and night already exist in map settings if i remember correctly
2) you can also change the schema files yourself, its quite easy. set the colors in /opt/waze/data/skins/default/night/schema and copy the new file as MyDocs/.waze/skins/default/night/schema . i promise to add it
3) please set the log level to 1 (search this thread for instructions) make it crash again and upload the log to the issue tracker in the waze-qt project at google code. i will check it out