Hello,
those are two separated issues, but you should be able to fix them easily.
Regarding the 403 while working on the template: please get inside the Configure WAF page and check the option Allow Site Templates. If I remember correctly, that's usually required by Helix templates.
If you still have the error, you should trigger the 403 error and then take a look at the Blocked Requests Log, looking for your IP. What's the reason for the block? So we can work from there.
Regarding Facebook comments, there could be two source for this issue. First of all disable both Admin Tools System Plugin and replace your current .htaccess file with Joomla default one. Are comments working now? If not, it means that the problem is not caused by Admin Tools.
Then enable the System Plugin again. Are comments working? If not, it means that while loading them, a security exception has been triggered, so you to follow the steps above (look for your IP address and write down the reason for the block).
Otherwise, it means it's a .htaccess issues. Most likely you have to add an exception inside the Htaccess Manager, more info here: https://www.akeeba.com/documentation/admin-tools/server-protection.html#determine-required-exceptions
Davide Tampellini
Developer and Support Staff
🇮🇹Italian: native 🇬🇧English: good • 🕐 My time zone is Europe / Rome (UTC +1)
Please keep in mind my timezone and cultural differences when reading my replies. Thank you!