If you verified your phone number on Binance, which I believe you did as a criterion to operate the account for six years, then what you should do is try to log in using your phone number and click on “Forgot Password.” You will be asked for a code that will be generated by Binance and sent as a text message to your registered phone number. Although I have not used phone number to change a password before, but a verified phone number is always another way to gain security access on most exchanges, and I believe this should work with Binance as well.
The issue is that if he wants to use new device to access Binance, Binance will send code to his phone as a message and email to be used for authentication. Also 2FA will be needed. He needs these three things before he can have access to his account.
I don't think recovering Gmail would be easy since he lost the phone, including his number, and I believe the phone number is also lost. So recovering Gmail isn't possible.
In my country, if you lost your phone and your sim card is lost, all you need to do is to go the service provider office near where you are and tell them that you want to recover back the stolen sim. If you have what came with the sim card when you bought it, they will do it for you. If you do not have what came with the sim, you can go for affidavit which may discourage some people but prefer to just block the sim and get another one.
If his email has recovery email, he can use that to recover the email.
But the problem is that he needs both the email and phones to have access to the exchange. He also needs his 2FA. So the best would be to just go through the process stated above already on the first post.