Nearing completion.  Have to do some revisions to the mag catch mold.

No.  I used a Hahn block in the Kp-15 with 9mm upper for some time before we started this project.

Use as heavy of a buffer as you can that still allows it to cycle reliably.   I like 8oz with .308 spring the best.

No to all of the above

Those would all be new dedicated molds.  

There is not enough of a mass market for those calibers and mag types to justify the tooling cost.

The KP-15 is commercially successful because any AR15 upper will work with it.

The KP-9 uses the cheapest most readily available 9mm magazines, and readily available 9mm Blowback uppers.  

Deviating from that makes it more and more niche, and a product more suitable for billet.   Are the people doing billet .45s selling tens of thousands?  I doubt it.   And accordingly it is not worth the development/tooling cost.