I think the knurl is unnecessary, smooth will give you finer starting and speed control. The 3' anvil should be OK if you're using bolt on dies. The top of my lower die is at 39.5", but I guess it depends on how tall you are.
Yes, they're used on presses, can be man powered like a flypress. I guess it would work on an air hammer if you can generate enough up force to raise the ram and extract the punch.
On most scroll chucks it doesn't matter which slots the jaws are in as long as they are in the proper sequence. If they're closing evenly they're in sequence. You have 3 combinations of slots they'll go in, check for best sliding fit with scroll out.