Postgresql – Postgres – Revoke database acess from user, but allow replication acess

There is no need to grant CONTROL on the schema.
The permission required to DROP SCHEMA is either CONTROL on the schema or ALTER ANY SCHEMA at the database level, and that is why your user was able to drop the schema. Removing these two permissions will prevent the role-associated users from creating and droping the schema (unless they have higher level permissions of course).

The required permission to CREATE ALTER and DROP other objects is the CREATE permission for the object type (table\procedure\function\view) combined with ALTER permission on the schema.
You already have these permissions in your script, so all that you have to do is remove the CONTROL permission. For reference, here is a BOL list of DDL statements where You can find the required permission for all object types.

For the lazy, here is your code after removing the unnecessary permission:

CREATE ROLE myrole AUTHORIZATION dbo;
EXEC sp_addrolemember 'myrole', 'myuser';

CREATE SCHEMA myschema AUTHORIZATION dbo;

GRANT ALTER, DELETE, EXECUTE, INSERT, REFERENCES, SELECT,
          UPDATE, VIEW DEFINITION ON SCHEMA::myschema TO myrole;

GRANT CREATE TABLE, CREATE PROCEDURE, CREATE FUNCTION, CREATE VIEW TO myrole;

If the users are administrators, there is no way to keep them out. This could be sysadmin on the server, dbo on the database, etc.

The easiest way to keep other (non-Administrator) logins out of your database is to never grant them rights or (as one part of your code suggests) drop any users that are not 'automacao' or some other needed service logins.

Also, rather than cycling through every securable, you can use (assuming SQL Server 2005 and forward) is to grant at the database level. E.g.

 GRANT EXECUTE ON DATABASE::YourDB TO automacao