Thanks so much, all of you, for the replies! 🙂
Arthur is doing well, eating lots and chattering away! He even was willing to step up on my hand from his cage door the other day 🙂 His cere doesn't seem to have changed too much as of yet, but I will give it more time. He's a handsome boy regardless! 😉
The Ivermectin might need a little more time to work well, and I will repeat treatment to be sure, as my vet recommended to do this too.