You wouldn't have mentioned "pitbull" in any speculation you might have had about Asher's ancestry? I suggest you never ever mention "pitbull" in connection with your dog in any public face to face place. Just so you avoid any issues with BSL (stupid law but you don't want to have to deal with all the conditions associated). If anyone else does, just say maybe a bit of Staffordshire - some of them come in brindle.
Like the others have said, the trainer's "temperment test" was idiotic and she's going to get her face bitten if she keeps doing it and it will probably be a tiny terrier with small dog syndrome that does it.
Do keep up the good work obedience wise. And if you can find a dog obedience club - that would be a fantastic way to keep things going. Ours even lets dogs that are a bit dog aggressive train, they just do all the moves at a safe distance to the rest of the class.