I spoke to the instructor about the problems I've been having. He told me not to worry. He said nobody gets this stuff at the beginning, and that I should concentrate on using the equipment for practical purposes. Once I had a feel for the mathematics, I'd be in a better place to understand the theory. I asked him how I was supposed to do anything with mathematics I couldn't understand. He said I should use the established models. I pointed out that the established models don't work, and he didn't seem to know what to say.
I've got a lesson in computer operation tomorrow. I don't think it's going to enlighten me. I don't think the instructor has much more of a grasp of the mathematics than I do, and I think that reflects the general problem: none of them know what they're doing. They enter numbers and receive results, but there's no science going on that I can see. Since their black box approach is no longer working, I'd expect them to be trying to change it. But no one I've met so far has the chops to do that. There must be some people here who know what's going on. They're the people I'm going to have to find.