> Would forwarding continue to work if your account is disabled or terminated? That doesn't seem likely?

No, but the idea is that you can point the domain at a new host and at least keep receiving future email, so that you don't lose the ability to password reset accounts, etc.

As for

> I wish there was a way to pay for Google (such as Google One) and it meant Google wouldn't ban your Gmail account

There's a reason I pay, like, €50 a year for my email hosting instead of gmail's free mail. I want to be able to actually reach a human when it comes to problems with my email instead of Google's customer service void.

That's why you need to own your domain. When they lock you out, you setup a new mailbox elsewhere and point your domain to it. That covers new mail. And the archives are still accessible because you've been forwarding mail all along.

you seem knowledgeable, is there a way to do this with every possible email address at your domain? Forward them all to that single other box?

Yes, and (for example) Fastmail allows you to do that very easily. So does Google if you prefer to keep the Gmail interface & are willing to pay for G Suite.

And, if your mail client’s UI allows, you can even send from <whatever>@yourdoma.in to avoid disclosing your “real” address when you reply.

My favorite use-case: you sign up for foo.com with foo@yourdomain.com. Then foo sells their contact database, and now you’re getting viagra spam all day. Ok, just add a filter to auto-trash anything addressed to foo@, and the problem is solved.

Not op, but what you described is called a catchall address. Easily done with custom domain. Basically a regex for *@domain.tld, every mail sent to (anything)@domain.tld will arrive at a preconfigured mailbox, say admin@domain.tld etc