I totally agree with you for the medium term. My challenge right now is that I don't have access to the DNS records and migrating to a new email service will take days/weeks.
Migrating to new email service doesn't take days/weeks, at best a few hours as long as you were prepared with existing email aliases (catch all can help minimize the missing aliases) and configuration and access.
In the short term, you are at the mercy of Google. Next time you want to avoid similar fiasco, when you purchase any service from a vendor, please consider the whole offering from sales to support. If you don't see a quick resolution pathway for situations when shit hits the fan, walk away from those vendors.
Personally, I have never bought or recommended others to purchase any "paid" services from Google. They are incapable of and not setup for providing enterprise level product, service and support.
How long it takes to switch services depends on how long you have your TTL set on your MX records. If he set it to expire after days or weeks, it would take days or weeks to switch services. Usually the default is a much lower value, but there are some legitimate reasons to want a high TTL (It could help mitigate a domain hijacking for example).
