"I wonder, too ... does Mr. Stallman's PC have a proprietary BIOS, or did he write that code, too?"
Yes, he uses a free BIOS.
Stallman is pragmatic, it's just that his line between pragmatic and unrealistic isn't quite where you (or I) would draw it. Before the Linux kernel came along, the GNU project had existed almost a decade - he surely used a computer then in order to write (or help write) the first versions of GCC, emacs, and a host of other essential free software programs. Now he doesn't have to, so he won't go back, and I'm sure he jumped onto a free kernel as quickly as it became remotely practical to use. Remember, GNU was working on a kernel of its own before Linux came on the scene. Again, this is not the pragmatism you or I might have chosen, but it is pragmatism. Same thing with FreeBIOS - he was in the news a year or two ago about switching the FSF over to computers that could run a completely free software BIOS. He's also been one of the many campaigning for free firmware, and the FSF has made that an important issue recently. CPU microcode? Haven't heard him talk about that yet, but I'm sure it will come.