You already found Vadim’s book, which is really the go-to answer if you want to understand this stuff.
The U-He blog has a lot of good stuff. https://urs.silvrback.com/zero-delay-feedback was helpful for instance.
I also found this repo (https://github.com/ddiakopoulos/MoogLadders) very useful. We are expanding the filter set in surge right now, and as a test case I copied his RK Ladder Simulator model and it sounds good. (I haven’t looked inside Fundamental VCF to see if the code is the same). While we have our own models we are working on and I don’t think we will ship surge with that simulator intact, it was helpful as a worked example of a filter infrastructurally.