Multi-tenancy Architecture

Does anyone have any feedback/insight on this SAAS model illustrated in the diagram? The goal is to automate as many processes as possible.

At the moment I have these Qs:

Do I have to manually point each front-end to a specific user's CMS portal and deploy to Vercel. Can this be automated by using this or a different architecture?

If I want to add more themes (available to prior and new users)... how do I safely and simply go about that?

I'd like to run 1 CMS server with many front-end servers, if viable. That way if the server goes down they're independent. Though if a different architectural approach is more suited I'm interested.

The goal is to automate as many processes as possible.

Can I use 1 front-end server too or will it be too slow/risky with over 50 users sharing?