I've just added "spawn on death hit" checkbox to Damage prefab section. Defaults to off.
For the other one, you'd like an incremental Vector3 or a random offset max Vector3? Please specify. Normally in most games I've seen, all death prefabs spawn in the same place then move away from each other with movement scripts...
I may add this real quick because it's easy. But I have a better more flexible solution in mind.
I'm about to add a new "Send Mode" to Custom Events of "Same Game Object". That way you could set up a Triggered Spawner wave on the same objects as the Killable and tell the Killable to fire that Custom Event when it's destroyed. That way you have all the extra options that Triggered Spawners have for spawning (more than just Incremental).
I had the same idea (adding to Damage prefab). Those will both be in the next version.
FYI, My idea with the Custom Events wouldn't require any scripting. There were a bunch of "Fire Custom Event" sections added in the last couple versions, including when Killable is Destroyed or Damaged