Añadir nuevas propiedades

Hello
I somehow messed one of my tables badly, so when I run Symfony console make:migration and all my files are committed (no changes) this migration is generated:

public function up(Schema $schema): void
    {
        // this up() migration is auto-generated, please modify it to your needs
        $this->addSql('ALTER TABLE recruiter DROP CONSTRAINT FK_DE8633D8D8A48BBD');
        $this->addSql('DROP INDEX IDX_DE8633D8D8A48BBD');
        $this->addSql('ALTER TABLE recruiter ALTER postal_code SET NOT NULL');
        $this->addSql('ALTER TABLE recruiter RENAME COLUMN country_id TO country_id_id');
        $this->addSql('ALTER TABLE recruiter ADD CONSTRAINT FK_DE8633D8D8A48BBD FOREIGN KEY (country_id_id) REFERENCES country (id) NOT DEFERRABLE INITIALLY IMMEDIATE');
        $this->addSql('CREATE INDEX IDX_DE8633D8D8A48BBD ON recruiter (country_id_id)');
    }

    public function down(Schema $schema): void
    {
        // this down() migration is auto-generated, please modify it to your needs
        $this->addSql('CREATE SCHEMA public');
        $this->addSql('ALTER TABLE recruiter DROP CONSTRAINT fk_de8633d8d8a48bbd');
        $this->addSql('DROP INDEX idx_de8633d8d8a48bbd');
        $this->addSql('ALTER TABLE recruiter ALTER postal_code DROP NOT NULL');
        $this->addSql('ALTER TABLE recruiter RENAME COLUMN country_id_id TO country_id');
        $this->addSql('ALTER TABLE recruiter ADD CONSTRAINT fk_de8633d8d8a48bbd FOREIGN KEY (country_id) REFERENCES country (id) NOT DEFERRABLE INITIALLY IMMEDIATE');
        $this->addSql('CREATE INDEX idx_de8633d8d8a48bbd ON recruiter (country_id)');
    }

My Questions:

1. My field postal_code in table recruiter is null, and I want to remain to be null. Why on earth generated migration "insists" to set it back to not null? What I have done wrong?
2. I have renamed the country_id_id in country_id and I want to remain country_id. Why the generated migration is "insisting" to return back the old name with id_id?
3. I had field named country, and I remove it, and I don't know if the IDX and the FK refers to that field or on some other. How can I prevent those "proposals" to show again and again in each generated migration?
4. I have read somewhere that on possible way to resolve such issue is to use the command symfony console doctrine:migrations:diff to generate the current SQL and then remove all migrations except the first one, and in the "up" method to add the generated code. However it didn't mention what should one add in the "down" method. Can this approach be used as a way to resolve messed up migrations?

We changed $votes property never to be null. So can we remove "?" in getVotes method (or this will provide errors during for example form saving)? And the same question about getCreatedAt method

concerning default values...
Am I right to understand that the way you've shown here (i.e. creating the entity > altering the code to insert defaults > not migrating the code changes), the table would still accept null values, but no value would ever be null because I changed the code?
If so, how could I make the table no longer accept null values? Should I run the symfony console make:migration command again? Or isn't there a way to do this once it's been set as nullable?