I never had any success with Magento 2 in a Windows localhost environment. Everytime I fixed one thing, something else would get in my way. Magento 2 is complicated enough as it is without adding these kind of variables to the mix.
Anyway, I don’t think the post you linked is relevant to your issue. The post says that a file needs editing (which it still might need), but in your case the file is simply missing. To me this suggests an installation issue. This might be one of many files that you’ve identified as missing.
But let’s assume for a moment that the Validator.php is in fact the only file that’s missing. You can get a copy of that missing file from Magento.
P.S. If you want to develop locally, due to costs or whatever, then I’d recommend learning how to use a VirtualBox. That way you can actually run a Ubuntu Server on a Windows machine. Therefore you’d be developing in an environment that mirrors the real thing - Rather than a simulation. It’s something worth adding to your developer toolkit.