Custom field Widget multiple values as a Table

Hello I created a custom field type and field widget with multiple values, one entity reference and two checkboxes.

Everything's was working well, but to improve the usability of the fields, I would like to display the fields as a table, and that is when my problem begins.

I tried changing the field widget to be like a table, that visually worked to me, but now I will have problem because the keys of each field will be different than the defined in the field type, any suggestions in how to handle with this problem? If i roll back and remove the 'multiple_route' key to create the table and set the $elements[''] like i orignally started the fields are saving correctly.

FieldWidgetType.php

class MultipleRouteWidgetType extends WidgetBase {

  /**
   * {@inheritdoc}
   */
  public function formElement(FieldItemListInterface $items, $delta, array $element, array &$form, FormStateInterface $form_state) {

    $element['multiple_route'] = [
      '#type' => 'table',
      '#header' => [
        t(''),
        t('checkbox 1'),
        t('checkbox 2'),
      ],
    ];

    $route_value = NULL;
    if (isset($items[$delta]->route)) {
      $route_value = \Drupal::entityTypeManager()->getStorage('node')->load(intval($items[$delta]->route));
    }

    $element['multiple_route'][0]['route'] = $element + [
      '#title' => t('Page'),
      '#type' => 'entity_autocomplete',
      '#target_type' => 'node',
      '#required' => TRUE,
      '#empty_value' => NULL,
      '#default_value' => $route_value,
    ];

    $element['multiple_route'][0]['checkbox_1'] = [
      '#title' => t('checkbox 1'),
      '#type' => 'checkbox',
      '#empty_value' => 0,
      '#default_value' => isset($items[$delta]->checkbox_1) ? $items[$delta]->checkbox_1 : 0,
    ];

    $element['multiple_route'][0]['checkbox_2'] = [
      '#title' => t('checkbox_2.'),
      '#type' => 'checkbox',
      '#default_value' => isset($items[$delta]->checkbox_2) ? $items[$delta]->checkbox_2 : 0,
    ];

    return $element;
  }

}

Visually this is my goal and worked:

But now the fields will not save because the keys are different than the definied in the schema, resulting in this error:

The website encountered an unexpected error. Please try again later. Error: Cannot create references to/from string offsets in Drupal\Component\Utility\NestedArray::setValue() (line 155 of core/lib/Drupal/Component/Utility/NestedArray.php). Drupal\Component\Utility\NestedArray::setValue(Array, Array, NULL) (Line: 1254)

Field Type.php property definitions and schema:

class RouteFieldType extends FieldItemBase {

  /**
   * {@inheritdoc}
   */
  public static function propertyDefinitions(FieldStorageDefinitionInterface $field_definition) {
    $properties['route'] = DataDefinition::create('integer')
      ->setLabel(new TranslatableMarkup('Page'))
      ->addConstraint('RouteConstraint', ['fieldName' => $field_definition])
      ->setRequired(TRUE);

    $properties['checkbox_1'] = DataDefinition::create('boolean')
      ->setLabel(new TranslatableMarkup('checkbox_1'));

    $properties['checkbox_2'] = DataDefinition::create('boolean')
      ->setLabel(new TranslatableMarkup('checkbox_2'));

    return $properties;
  }

  /**
   * {@inheritdoc}
   */
  public static function schema(FieldStorageDefinitionInterface $field_definition) {
    $schema = [
      'columns' => [
        'route' => [
          'type' => 'int',
          'unsigned' => TRUE,
          'not null' => TRUE,
        ],
        'checkbox_1' => [
          'type' => 'int',
          'size' => 'tiny',
          'unsigned' => TRUE,
          'not null' => TRUE,
          'default' => 0,
        ],
        'checkbox_2' => [
          'type' => 'int',
          'size' => 'tiny',
          'unsigned' => TRUE,
          'not null' => TRUE,
          'default' => 0,
        ],
      ],
    ];

    return $schema;
  }

Thank you.

Before that to quick solve the issue and because my task was late, i emulate the form table with a markup on the suffix and prefix on the widget fields and returned the keys to the root of structure of $element:

public function formElement(FieldItemListInterface $items, $delta, array $element, array &$form, FormStateInterface $form_state) {
    $prefix = '<table class="responsive-enabled">
      <thead>
        <tr>
          <th></th>
          <th>' . t('Checbox 1') . '</th>
          <th>' . t('Checbox 2') . '</th>
        </tr>
      </thead>
      <tbody>
        <tr class="odd">
          <td>
    ';

    $route_value = NULL;
    if (isset($items[$delta]->route)) {
      $route_value = \Drupal::entityTypeManager()->getStorage('node')->load(intval($items[$delta]->route));
    }

    $element['route'] = $element + [
      '#prefix' => $prefix,
      '#suffix' => '</td>',
      '#title' => t('Page'),
      '#type' => 'entity_autocomplete',
      '#target_type' => 'node',
      '#required' => TRUE,
      '#empty_value' => NULL,
      '#default_value' => $route_value,
    ];

    $element['checkbox_1'] = [
      '#prefix' => '<td>',
      '#suffix' => '</td>',
      '#title' => t('c'),
      '#title_display' => 'invisible',
      '#type' => 'checkbox',
      '#empty_value' => 0,
      '#default_value' => isset($items[$delta]->checkbox_1) ? $items[$delta]->checkbox_1 : 0,
    ];

    $element['checkbox_2'] = [
      '#prefix' => '<td>',
      '#suffix' => '</td></tr></tbody></table>',
      '#title' => t('c.'),
      '#title_display' => 'invisible',
      '#type' => 'checkbox',
      '#empty_value' => 0,
      '#default_value' => isset($items[$delta]->checkbox_2) ? $items[$delta]->checkbox_2 : 0,
    ];

    return $element;
  }