Hi, Jonas
Definitely you're going to need some more snaps, attached is a diagram for snaps placemment so you can calculate how many are needed. You can use it for the Han snap too, about the Belt what I did was to use this kind of snap to attach the canvas belto to the ab and another type,(look at the image) to attach the plastic belt to the canvas . But refer to the building threads and make a better decision.
Rivets I have used to attach the plastic belt to the canvas :
Hope this can help. you are doing a great job mate!!