I'm left wondering what to think of this one. I think it was a good choice to approach it from an outside character's perspective, but it feels remarkably out of place for Deni to just throw those details out there like that. From earlier reading, I had the impression that before he met Ignis, he played things close to the chest. However, things are different and he's feeling guilt he isn't used to, so breaking away from the norm is explicable, just unexpected.
Seeing what a disaster Deni is making of the forge, it's no surprise he would drive away the more fastidious gunsmith. The fact that Midilia was so tolerant came as another surprise.
One complaint I have, though, is that the crafting portion feels like an afterthought. Mechanically there's no rule against it, but when I saw the [Craft] tag, I was looking forward to seeing what sort of ideas you had come up with to handle the task given. When it comes down to it, I think the only thing I got out of the descriptions were that he made a bigger gun to shoot a bigger bullet. At first I thought he was going to somehow use the folium, haha.