How to hook_views_query_alter arbitrary field and use it in view GUI
You could add a normal number field to the user profile in the drupal ui, then translate the rogue column into this normal drupal field by populating the field from the table column with an SQL query (or several queries via a looped php script) on your database.

This would mean that the field would become available in the normal drupal way within views, and would also avoid you having these sorts of issues on another occasion.

I am sure it does not need to be said, but obviously you would backup first and perform this operation in a local development to test.

Note: It should even be possible to export the numeric value against uid and use feeds to bring the value into a profile2 field using the uid as unique, if that felt more comfortable than the naked sql population.