DaemonUmbra

1.12 is no longer supported on this forum. Please update to a modern version of Minecraft to receive support.

Please provide a log from your run without mods

Well that makes it a bit hard to verify issues when your host could be doing whatever the heck in the background without you knowing

I would suggest getting a dedicated graphics card so your CPU and RAM aren't pulling double-duty

I don't know what you used to post the log here, but next time please upload the log to a paste site, this is horrible to look at with all the formatting removed One of your server configs is failing to load properly, if you have not modified it delete ironfurnaces-server.toml

Did you download the server-specific files for the pack or did you copy the mods from the client and hope?

1.12 is no longer supported on this forum. Please update to a modern version of Minecraft to receive support.

How are you starting the server? If you're using scripts, please provide them

First I suggest re-doing your repositor(y/ies) to take advantage of git branches and to separate your projects properly Second, do you understand the code you copied?

1.12 is no longer supported on this forum. Please update to a modern version of Minecraft to receive support.

Please read your errors

Try removing Optifine

Reporting a RAM issue without giving hard numbers isn't all that helpful if I'm honest, can you run a Java profiler or something?

What launcher are you using?

Optifine not being compatible with Forge is not on Forge to fix. Regardless, please refer to Optifine's changelog for compatibility information (I believe one or more of their pre-releases has tentative support)