Hello,
I hope it is ok to make a bit of advertisement here for my project, but I guess some of you might benefit from it.
Some month ago I developed a little program which allows you to use a second keyboard for macros on Windows. It is early alpha, but it seems to work pretty well. You can define commands which should be executed on a specific key (on a specific keyboard). It is also possible to passthrough a keyboard, however this has some limitations yet.
You can find the project here: https://github.com/lal12/macroMyKBD
If you tested it, and have problems, feature requests or other feedback, feel free to response to this thread or even better create a ticket/issue on the linked page.