1) Call your cellphone carrier and ask to set up a password/PIN to be used for when you call into the customer service phone number.
2) Consider your phone number and SIM card insecure. The phone carriers are ignoring the SIM swap problem even though they know how much damage it's causing. Give your phone number to as few companies as possible. Phone services such as Google Voice work without a SIM card, so they are less prone to problems. Give out such a phone number if necessary.
3) Don't use text message verification codes as 2FA. Use an authentication app, such as Google Authenticator.
4) You can retake possession of your hacked Gmail account by providing one of the previously used passwords. No need to have a working phone.
5) Ask yourself, what will happen if you lose both your laptop and your phone at once? Do you have things set up in a way where you can get back into your digital life? Someone can break into your home while you're away, the government can confiscate them at the airport, etc.
6) Check what email addresses you have configured as backup auth methods for your Gmail. Those accounts can be used as a means of access by a hacker.