In the already started world, try reverting your section about skin colors. I think maybe you have dwarves who are already set to have skin colors from the default list, and if those colors aren't on the new steel skin color list, I think it might cause crashy problems.
Also, as far as loving that embark spot, if the above change doesn't fix things, or you're dead set on getting those steel colors into your dwarves, try this:
Make a backup of the save folder.
Revert the raws.
Abandon the Fortress.
Load the region in legends mode.
Export the world gen parameters. The text file for them should appear in the main DF folder.
Put your mods into the raws in the main DF folder. (I suggest doing it now, rather than between world gen and embark, because I expect npcs/historical figures will have their skin colors set. Doing this will probably alter how history plays out, since dwarves would be much tougher).
Copy the text from the world gen parameters for your world into world_gen.txt in the embark folder. Change the [TITLE:] tag to something you'll recognize.
In DF, Generate New World with Parameters.
Select the world gen parameters with the title you made.
Alternatively, if you want the same/relatively the same history but with your different skin colors, you *might* be able to change the raws for JUST the skin color first, generate the world, and then change the raws for the skin consistency (i.e. steel instead of skin).