Can I rename the "Unoffical Skyrim Legendary edition patch" esp and ini files to simply USLEEP? I know the ESP wont cause problems as I pretty much rename all my Morrowind mods, but does renaming an ini file break the mod in any way?

Why would you want to do that? There are potential problems with doing this. For instance, many mods require USLEEP as masters and if you rename it you will have missing masters and your game won't load if you have any mod in your load order that requires USLEEP as a master. You would also need to rename the bsa, or the USLEEP assets won't load. There may be other issues as well. I see a lot of downside here with no upside.