I think you are on the right track. The first thing you will need to do is change the status array so that it also checks for actor.id. You will then need to create an instance variable in your HUD which tracks the ID of the current party member. You can initialize it as 0 in the initialize method and for the purpose of the rest of the post I'll say it's @member_id.
Then, when you retrieve the actor in the update method, you do so through $game_party.members[@member_id].
Now all you need to do is add checks in the update method above what you have now for whether the player has triggered 1, 2, 3, or 4. If 1, change @member_id to 0, if 2, change @member_id to 1, etc... I haven't used YEM Keyboard Input before, but I assume it will let you check for those keys.
Discord
Light Style