The Db users in Octane can be a bit confusing, sometimes the installer can complain about too much permissions or too little. The permissions required for the Octane SQL ''power user'' are ''securityadmin'' and ''db_creator'' roles. Here is what I would try, it is usually easier to setup one power user for Octane and then let the installer create the other basic user.
First I would setup a user to be the ''power user'' in your case it looks like you are using ''ALM_Octane_DBAdmin'' I would verify that this user has only the ''securityadmin'' and ''db_creator'' roles and not any additional roles. The entries for the ''Power User'' in the setup.xml are the following:
''DBAdminUser'' The username of the SQL ''Power user'' goes here
''DBAdminPassword'' The password of the SQL ''Power user'' goes here
Those are the only places that you have to put in the information for the ''Power user.'' The next SQL user to consider for Octane is the ''DBLoginUser'' the easiest way to think of this user is the same as the ''td'' user was in regular legacy ALM, this is the database user that is used for day to day project operations. The easiest way to create this user is to let the installer create it which is where I think you were running into issues. I believe that yours was probably failing when trying to setup this user maybe due to the ''Power user'' not having the ability to grant permissions to the ''DBLoginUser'' when it was created. The entries for the ''DBLoginUser'' in the setup.xml file are the following:
''DbLoginUser'' This is where you put the value for your ''DBLoginUser'' this can be a user that you already have created or you can let the installer create it for you for this I usually use the value ''TD'' and let the installer create it for me to ensure that it has the correct permissions
''SchemaPassword'' This is where you put the password for the ''DBLoginUser'' if you are letting the installer create this user then just put what you want the password to be for the user, if the user already exists then put the existing password for the ''DBLoginUser''
If you keep having to run the installer over again you might want to clear out and delete what the installer has already created. So for instance if your installer got to the point of creating the site schema you might want to drop that database before you run the installer again since it is set to ''CREATE_NEW'' Also if you are letting the installer create the ''DBLoginUser'' then you can also delete it and allow the installer to recreate it again.