Count the number of results of a free text field if they are similar
I'd use taxonomy terms and the tagging feature built into drupal. There's an example of it on the Article content type that comes with drupal's standard install

So a user can start typing a term and the autocomplete will appear if that term already exists. The user can select it if it exists already. Otherwise when the node is saved the term will be created. You can select multiple terms by comma separating them exactly as you mentioned

Then getting a count of terms will be much more straight forward and should be do-able in views as each time a term is associated to a field it's stored in the database