neat, i've had a go at solving this issue earlier this week as well, went through several totally different iterations so i know how tricky it is, maybe by looking through this mod's code you might get an idea on how to lower your on_ticks, i'd also like to point out listening to circuit signals can be done with a trick shown in my thruster control behavior mod, if you tie that to a product finished signal or something you might be able to squeeze more performance out of it.

https://mods.factorio.com/mod/quality-holmium-ore-returns-more-holmium-solution

Cheers! It's pretty clear my current approach needs a lot of work. I wonder if it's actually possible to handle all fluids like I'm trying to do, without nuking performance.

yea its incredibly tricky to find something that works, is user friendly, and performant