Whenever I try to use Canvas caching I run into an issue I don't yet fully understand that causes my images to come out of cache blocky and terrible looking. Something about a max canvas size? I don't quite get it. Happens whenever I use fabric.js caching.

I'm guessing that means you rolled your own canvas API code, rather than using a library like PixiJS. Is that something you'd consider open-sourcing, or is it so tightly integrated with game-specific logic that it wouldn't make sense?

Yes, no helper libraries and I coded quite close to the metal.It's probably even a stretch to call it an engine. It's just built around the specific game mechanics. It wouldn't make sense to open source that part unfortunately.