My focus on licenses so far only really concerns making it easier for vendors like the OEM to use my library. When I open-source hardware layouts, I now know I need to investigate license details for hardware-specific language. (I don't have any control over the hardware in this case.) I don't mean to imply that I've fully solved the issue yet, just to draw attention to it being even more complicated than expected.
I've also noticed that, while the ISC doesn't specifically address binary distribution the way the BSD license does, the zlib license specifically notes that its copyright conditions apply to source distributions, so it seems like an even better choice in this specific case.
My point in general was that it seems you are still just attacking this one issue at a time, instead of realizing "oh, maybe there is a lot of other things I don't know", and asking for semi-professional help from someone.
By doing this, you make the problem worse, not better.
I'm not suggesting you hire a lawyer, there are actually plenty of places with qualified people often willing to help you figure out what issues you will hit.
I've also noticed that, while the ISC doesn't specifically address binary distribution the way the BSD license does, the zlib license specifically notes that its copyright conditions apply to source distributions, so it seems like an even better choice in this specific case.