As the title says, I'd like to request a mod that allows Skyrim to run in Fullscreen Windowed (borderless) mode AND does not pause Skyrim during wait/sleep when I alt-tab out.

Have you tried using control+shift+esc to open the task manager, thus minimizing the game instead of alt-tabbing so it doesn't pause during wait/sleep? This doesn't exactly answer your question but it may be an alternative.

That works? Interesting....