Hostinger just confirmed that making changes to the /.well-known folder with .htaccess is not possible on their shared hosting plan, so I can't set the CORS header on the stellar.toml file. So it looks like I need to find a new web host. Here is the official response I received:
"The .well-known directory is server-default, so that is why overriding and making changes to it is not possible on a shared hosting plan, as important data/information is stored there. To make meaningful changes in this directory, you would need root access, which is only available on our VPS plans."
Has anyone had success with another shared hosting provider?