The inevitable conclusion to this arc makes it very hard to accept any degree of tension here - it sucks having to ground how much I like Ash's Goodra in knowing that it will go away next episode, it puts a downer on every scene that shows how great a Pokemon it is. One of the best personalities on a Pokemon in a while, with a great backstory and plenty of room to develop with Ash and the other Pokemon, so obviously it has to go.
Let's just be glad that Kenzo is around, since it sets up a similar situation to Satoshi's Glion where it can come back for the League if necessary.
No idea. Anyone with villainous acts usually has a reason behind their attacks such as defending their territory from intruders.