How would I configure an Event with varying inputs and free registrations based on contribution level?
I think the discount codes is a good approach.  To do this all on one page would require either webform_civicrm for Drupal, which you don't have, or to write an extension.

If you write an extension, I'd use hook_validateForm to make the Logo/Display Name optional/required, based on their level.  The same hook would also allow you to set a maximum number of additional participants to register.  You can also add a jQuery script with hook_buildForm for niceties like adding/removing an asterisk as fields become required/optional, but you still need server-side validation for security purposes.