To be easier for you please follow the next procedure: https://vsaiyan.info/2018/01/09/solved-vcenter-appliance-root-partition-100-full-plus-unable-to-log-in-to-the-root-accou…
Maybe the log to clean is not the same but it will help you entering the GRUB and do the cleanup. Also the Enable BASH Shell is to access the console from inside vCenter, not to login using SSH. So if inside the console you trigger Alt + F1 you will jump to the BASH Console.
However i still think that you need to follow the procedure mentioned above as you probably will not be able to login there also because of the root parition being full.
