since there are THREE blocks in the crafting recipe and it's a 3:2 ratio it should be 18 Dark Iron Ingots.
No it shouldn't. In normal factorization, you only got 4 dark iron ingots from 1 dark iron block, GET YER MODS RIGHT.
OK, to be clear 3 iron blocks creates 2 Dark iron blocks when these are crafted they make 4 dark iron ingots 2 x 4 = 8 so 27 iron = 8 dark iron.
I am not sure if this is possible with the current custom crafting system or if sk wishes to implement this, but wouldn't it be more realistic if we were allowed to craft wraith lighters, but they cannot light anything on fire. Instead you place a wraith lighter w/ a iron block in the crafting table, and it would allow you to make a dark iron block while using some durability on the lighter. We will also be able to craft the lamps which require a lighter in the recipe.
How about if we set it up so that you can craft the lighter, but it doesn't work. However if you die with it in your hand and your head is dropped any iron blocks within 3 blocks of the fallen head burn with wrath fire and turn into dark iron. This would encourage a new section of the bazaar where people with vorpal swords could help those with lighters make the dark iron in a community setting.
This also sounds like a good way for peoples bases, or even spawn or other sections of the bazaar to get damaged (accidentally or maliciously). Ideal way would be just to craft it using 1 iron block and the lighter, using durability (similar to saws for making micro blocks), but that's just my opinion.
The spread can be turned off in the config; why don't we just do that and only make it so people can light it in there own region i am sure that would be simple enough.