If you are trying to restore your connection to your blogger account, deleting the Website Builder won't do that. Once the new site is connected, it won't redirect back to your old site unless you manually change the settings in what's called your DNS Zone File on your domain.
Depending on how you set it up before, you could reconnect by changing either the A record or forwarding the domain. Here are instructions on how to make the changes:
As for what changes to make, that depends on your blogger account. Usually, somewhere in your profile settings they will offer instructions on how to connect/use a domain registered elsewhere. Those are the instructions you want to look for. They will tell you what to change, and the instructions above will tell you how to change them.
I hope this helps!
If you have a template in place, that would be a reason why it's not letting you save the changes you're trying to make. Things like security, site protection, and 3rd party hosting can interfere with your ability to edit records.
Without seeing a copy of your records, it's hard to know what it is going on. It sounds like you have the right idea, but you might need to reach out to Customer Support to have someone look at your settings and see if there would be something interfering with your changes.