The installer code on GitHub does nothing because it is an empty shell.
You should not need an installer for mods, their installation should be as simple as dropping a jar file into the mods folder.
For a config file I would suggest Forge's @Config annotation, "for every block" still needs some interpretation though, do you mean every block of that kind will reference the same value or every block of that kind will have that variable but the value may be different from individual block to individual block?
I should mention that it's important that the debug.log come from the same run as the Java Error.
You can be sure by clearing your logs folder then running the configuration that crashes again, if the debug.log appears after that then it's come from that same run, if it's not there then your game is crashing before it even starts logging.
I mean is the Error Log from Java itself the only thing you have or is there a debug.log in any of your log folders?
By this I mean a debug.log from the same run the Java Error Log came from.
Do you have any logs besides this?
I suspect that while you may have an nVidia card, Minecraft could be ignoring it and using Intel Graphics which seem to be frequently faulty.
You appear to have a rogue unknown character immediately following the closing curly-brace for the jei dependencies block, guessing that was accidentally included in a copy-paste.
In the future please provide a full debug.log when you come here with an issue.
Though in this case I've seen this particular error enough to know you have Decocraft2, but not PTRLib, a mod it depends on.
Are you sure you aren't in the 1.12 section of the downloads rather than 1.12.2?
Edit: There is a section 1.12 containing subsections 1.12, 1.12.1, and 1.12.2, make sure you're in the right subsection.