Some consultant could fix your account (either by knowing how to fix the subaccounts or knowing the magic incantation to tell AWS to kill them) but of course it would cost much more than simply paying the bill.
Amazon rightly is very careful about closing accounts. This is why you have had a hard time thus far. When you say “invalid email accounts”, what do you mean? Are they perhaps addresses on a domain that you control? If so, it’s a very simple fix. You just re-create those addresses, then go through the “forgot password” process to regain access to those accounts.
If the addresses are on a domain that you do not control, well, that’s a lesson learned for you I think. In this case, you’ll need to continue working with support to explore what can be done.
Sounds like "neverending charging bonanza". Like one sh*tty bank I'm dealing with right now.
> Will they come after me for this?
You'll probably be fine.
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In the parent org account go to https://us-east-1.console.aws.amazon.com/organizations/v2/ho... and you can delete the child account and you should just be on the hook for the 90 days closure period. I think you can also just disassociate (revoke the invitation or similar) the account from the same place.