Can the account name of 'distributor_admin' be changed?
No it can't be renamed.  The good news is that the account only exists on the distributor, which doesn't really contain any user data.

You can safely disable the account when you aren't setting up new replication publishers. If you need to setup a new publisher, enable the account setup the publisher then disable the account again.

It does need to have sysadmin rights. It needs to be able to create linked servers.