Populate Radio Buttons Fields

You aren't going about things the correct way.

If you want the link to the page to pre-select the correct radio button then the link needs to pass the parameter and the value for that field in the query string.

Instead of this:
http://www.mydomain.com/site/?2

It would be this:
http://www.mydomain.com/site/?pacote_encomenda=2

You have to pass the parameter name you created and then the value you want to set it to and that value has to match one of the available choices for that field.

As for the shortcode, you wouldn't add field_value='pacote_encomenda=1,2,3' to the shortcode. What that is going to try and do is dynamically populate the field with the parameter pacote_encomenda with a value that equals "1,2,3" which doesn't exist.

If you are populating the field dynamically via the link to the page, you don't need to do anything to the shortcode that displays the form.

Instructions on how to dynamically populate a field can be found here:

http://www.gravityhelp.com/documentation/page/Using_Dynamic_Population

PLEASE NOTE you don't use all of the methods. You are either going to use the query string method, the shortcode method or the function method. You aren't going to use a combination of these like you are trying to do.