Hi João,
From what I understood you want to show the different inputs based on the option chosen on the dropbox.
One of the things that I noticed based on your OML was the lack of using your variables to show or hide the inputs. So what I did was to wrap the inputs inside IFs.

Another thing was to simplify the action used on the OnChange

So i added a new action where i have changed the code:

I have uploaded a new version of your OML.
I hope this helps to resolve your issue.
Best regards,
Bruno Gomes