How can I include CiviCRM relationships to node creations screens?
Your query seems a bit off to me. Focussing just on the portion of it that retrieves the employers of the logged in user wouldn't you have something like:
Select employer.id, employer.display_name from
civicrm_contact employer inner join
civicrm_relationship r on r.contact_id_b=employer.id
where r.contact_id_a=$current_contact_id limit 0,10;

(If your user isn't logged in, then I would just drop the where clause to populate the select widget with all employer orgs.)

IIRC the employer is the b contact for the relationship, not the a - might want to check that.