I thing you have it setup correctly. The enable_sso setting on Discourse is the one you need to have checked. It’s for using WordPress as the SSO provider for Discourse. The Discourse enable_sso_provider setting is for using Discourse as the SSO provider for another site.
Your settings on Discourse should look like this - with a better sso_secret:
Usually when this happens it’s because there is another plugin on your site that is performing a redirect after login - redirecting users to your homepage. Do you have any plugins that could be doing this?