Below is a screenshot of the root directory of a WordPress install. When you type www.yourdomain.com/wp-admin you are really loading www.yourdomain.com/wp-admin/index.php which in turn loads /wp-login.php in the root folder along with a number of files in all of these folders. Some are checked, some are loaded, some are referenced when WordPress initializes.
My recommendation is to keep WordPress and Wix totally separate from each other. When you are ready to launch your WP site, let everyone know the day has come and do the unveiling. Until then, keep them separate...
Another choice would be to install WordPress in a separate folder such as in www.yourdomain.com/wp In that case you may have better luck with redirecting from your root folder. I still do not recommend it.
I am not an expert on .htaccess nor on WordPress. My recommendation is based on my personal experiences.