First off from Toronto, Ontario, Canada.

If you are wearing the kilt to a formal event, I would strongly recommend against the sport kilt, while they are fine for what they are, they are not formal kilts, or even a reasonable facsimile, the USA Kilt Semi Trad. would to my mind work better for that kind of situation, and it would work for other events as well.

As to the belt, if you are wearing a P.C. Jacket and waistcoat, then the belt is not needed the problem is that if you wear a waistcoat with a belt then the belt tends to make the bottom of the waistcoat jut out and you don't want that.

I'm also not sure about the boots you are referring to but I don't think any boot would look right with a P.C. you would be better off with dress shoes.

I know that sounds like a lot, but really it isn't best of luck with it let us know how it goes.