While i´m no dev of Terraincontrol:
If it runs, it should be safe to use.
TC doesnt do much (not nothing, but not much) more than world Generation. You dont even need TerrainControl installed if you wish to use a Pregenerated world.
There is at least one working build for 1.12 on the Build server.
Development is veeeeeeery Slow.
Didn´t see any actual devs around the Forum for a while. So I´m not sure how much there is still development going.
Also, theres a Fork/spinoff of TerrainControl around, going strong. But thats definitely not working for 1.12 yet.
Also, if you are starting to create a world, and run in issues later. Try to use some Linebreaks and dont pack it all into a solid wall of text. Its hard to read.