1)Collars are used without exception. Except, not even high ranking officers want their children live with them. So some either hide it or smuggle them outside to give them a chance at life. And it will be a key point to several important NCPs. And Grinnoc puts a lot of effort that uncontrolled mages are considered public enemy #1.

2)Knighthood. For reasons yet unknown, Grinnoc is very paranoid about any worshiping/religion popping out. And he has a very good reason for this.

3)No, not really. Magic healing is used extensively, where regular fails. One of the main reasons mages were kept around, albeit leashed. Dwarves lead the forefront of technology, and consider the medical technology be something like 17-18 century. Decent understanding of anatomy, and how to fix obvious things like broken bones/limbs, sewing up wounds. Germs/Infections/Diseases are still not discovered, hence magic is used as a crutch.

4.Luminous Knights operate on honor first and foremost. Being a shining example to others, protecting those who can't protect themselves, etc. Though not everyone buys into those ideals, some do believe in their cause deeply. And as mentioned before, any attempts to find some sort of explanation for Luminosity via faith are swiftly and brutally silenced.