wp-config.php includes files, it’s not just a config file, and WordPress isn’t built to allow putting the file 2 levels up.
However, WordPress already supports loading wp-config.php from 1 level up.
With all of this in mind though, this is only really a protection if you’re worried about mis-configuring your server. Unless PHP execution is turned off, which would be a major issue in of itself, wp-config.php won’t leak any information.
this gave me white screen of death on admin pages and some other pages
A WSOD is a HTTP 500 error code, to see the real error message you have to look in the PHP error logs. It’s the difference between a plane disappearing, and finding its flight recorder/black box.