Nice you managed to make it work :)
Now, about the MythAtelier plugin, you probably need to find where the plugin specifies that LUK is used for calculations and replace with a custom parameter. The thing is, even if there is a plugin parameter that you could change, this probably needs to be adjusted on the plugin code too. And since it is a paid plugin, I can do nothing on my side.
You can try talking to the developer, by opening a thread there and requesting compatibility. My plugin is free and the code is open, so he/she can take a look (or talk to me) so we can make a compatibility.