Thank you so much everyone, this is something I've worked on for a few years on and off -- I posted about it here in a Show HN a few hours ago [0]

The biggest unlock was finding Willy McAllister's excellent Circuit Sandbox [1], which provides the Minivac Simulator's underlying electrical math. I tried so many approaches to simulate electricity (a doomed DIY approach, Falstad, Spice...) but Circuit Sandbox's DC analysis did the job perfectly.

Ping me for questions, and would love to read your feedback!

[0] https://news.ycombinator.com/item?id=45945762

[1] https://spinningnumbers.org/a/circuit-sandbox.html