hanging debate -
I would think that you could utilize more space by hanging as opposed to having dead space between the racks. I also noticed that the racks leave impressions in the product if that matters to you. Although, if your smoker has hot spots, you could potentially rearrange more easily with racks than if all links are threaded over sticks, as opposed to hung on hooks.
I don't know how much pepper to add.
I am not seasoned pro, but with the sausage i have made, it was easy to eyeball the lean content of the trimmings. What I mean is that if you ask your butcher for 50/50 and you look at it and it seems to be more like 75% fat, then add a little more lean.