Also the custom races appear to use the generic custom race star systems and not the specified ones in the CustomRace.xml.
The default 'custom race' star system isn't used because it's not actually properly linked (star names in raceconfig and custom planets are mismatched, IIRC). If the game doesn't find a system definition matching the reference in raceconfig, it generates a default 10/4/0/0/0 system named for the race, as you've experienced.
Custom star systems do work properly if you correctly link the names, last I checked.
Do bear in mind that if you change a race in RaceConfig.xml directly, you need to delete any corresponding .customracexml files from My Documents\My Games\GC2DarkAvatar before the changes will be reflected in the game (those files contain in-game customizations and override the raceconfig.xml settings).