The adamantine skin thing is pretty easy, actually. Find the bottom of the dwarf entry in creature_standard.txt and paste this in:
[SELECT_MATERIAL:SKIN]
[SPEC_HEAT:7500]
[MELTING_POINT:25000]
[BOILING_POINT:50000]
[SOLID_DENSITY:200]
[IMPACT_YIELD:5000000]
[IMPACT_FRACTURE:5000000]
[IMPACT_STRAIN_AT_YIELD:0]
[COMPRESSIVE_YIELD:5000000]
[COMPRESSIVE_FRACTURE:5000000]
[COMPRESSIVE_STRAIN_AT_YIELD:0]
[TENSILE_YIELD:5000000]
[TENSILE_FRACTURE:5000000]
[TENSILE_STRAIN_AT_YIELD:0]
[TORSION_YIELD:5000000]
[TORSION_FRACTURE:5000000]
[TORSION_STRAIN_AT_YIELD:0]
[SHEAR_YIELD:5000000]
[SHEAR_FRACTURE:5000000]
[SHEAR_STRAIN_AT_YIELD:0]
[BENDING_YIELD:5000000]
[BENDING_FRACTURE:5000000]
[BENDING_STRAIN_AT_YIELD:0]
Material traits were taken from inorganic_metal.txt. I trimmed away the bits that won't really matter for a temporary thing.
Of course, adamantine skin won't actually save you from blunt impacts, but nothing is going to cut through that dwarf skin. If you want a normally-invulnurable dwarf, use this:
[SELECT_MATERIAL:ALL]
[SPEC_HEAT:500]
[MELTING_POINT:12718]
[BOILING_POINT:14968]
[SOLID_DENSITY:7850]
[IMPACT_YIELD:1505000]
[IMPACT_FRACTURE:2520000]
[IMPACT_STRAIN_AT_YIELD:940]
[COMPRESSIVE_YIELD:1505000]
[COMPRESSIVE_FRACTURE:2520000]
[COMPRESSIVE_STRAIN_AT_YIELD:940] 160
[TENSILE_YIELD:430000]
[TENSILE_FRACTURE:720000]
[TENSILE_STRAIN_AT_YIELD:225] 200
[TORSION_YIELD:430000]
[TORSION_FRACTURE:720000]
[TORSION_STRAIN_AT_YIELD:215]
[SHEAR_YIELD:430000]
[SHEAR_FRACTURE:720000]
[SHEAR_STRAIN_AT_YIELD:215] no data, used 200
[BENDING_YIELD:430000]
[BENDING_FRACTURE:720000]
[BENDING_STRAIN_AT_YIELD:215]
[MAX_EDGE:10000]
[SELECT_MATERIAL:BLOOD]
[PLUS_MATERIAL:PUS]
[PLUS_MATERIAL:SWEAT]
[PLUS_MATERIAL:TEARS]
[MELTING_POINT:10000]
This makes your dwarves out of steel. Adamantine weapons will still cut, but no wereiguana will do anything significant. Coincidentally, your dwarves will also punch like steel maces. Because they are steel made of steel. Modding is fun.