I'm not sure what about this people are worried about.
Grinding on the calipers where he did isn't going to hurt anything, there's plenty of metal there.
Grinding on the brackets where he did isn't going to hurt anything, those aren't a high strength component anyway.
The small gap at the wheel isn't a concern, lots of cars run tight clearances there.
Good on you for the initiative! Big brake "Kits" are insanely overpriced.