Had a similar issue with GCP (for a much larger amount) two years ago. Mistakes happen. In the end it took 3-4 months before the credit showed up in our billing account.

In my experience GCP does not want to bankrupt customers for some out of control API calls.

Keeping paying your invoices while excluding the huge amount you cannot afford. I think your fears of account suspension are overblown as long as you have an active billing dispute and are otherwise current in your billing account.

Also you have to do your part to avoid repeating this mistake. In the absence of better cost-based controls -- make sure your quotas are brought _way_ down to control usage.

Also add alerting including an escalation to something that will wake you up on nights/weekends like PagerDuty.