I FIXED TY_FnHFreeSkills.js BY MYSELF
Well, in your normal plugin, when you select the character the function of addActor call the function created by the plugin that verify and set the const LeaderID to the party ID. But there is a problem with it.
In character Select menu, when you select a character FIRST the character of your selection is added to your party, and AFTER that Levi (in game Party Start Character and actor 1) is removed from your party.
BUT, if we check this after the Levi being removed from our party, the const LeaderID will receive the Correct Actor. I think I'm going to be the new plugin developer of this page in this rhythm.