Are they not the same..?
However, you might be able to use Centred# Global commands OR UOFiddler Map Copy which should be the way to go as its basically going to be the same XY
1 - Centred for sure. I think people also use DragonMap to make full maps.
2 - Most of your "Custom" files should be imported within C:\YOUR_SERVER\Scripts\Custom
3 - Look up "ExpansionInfo.cs" within your ServUO files
I personally do not use this for Unchained but after giving a quick look you could just add the main codes from the EventSink from the achievement (when looting) to
Daat99MasterLootersUtils
Right after the items are being sent to the backpack/or master lootbag
Thats a better approach, your initial post would only trigger the effect upon mobile creation.
Might want to add a delay so its effect is not constantly spammed if alot of people are around the NPC, if you want something as a base for the delay you can take a look at SandVortex.cs
Im hoping youre not manually modifying your map.. that sounds like a struggle
However, to find item IDs, you could get UOFiddler
https://www.servuo.com/threads/uo-fiddler.13524/