Thank you for your question and sorry you had to wait so long for an answer!
Since you have a 5 years residence permit, you are allowed to travel within the Schengen Area without visa. Getting married in Malta should not be a problem.
Here is a page concerning weddings in Malta and the documents, which are required to marry. These are:
- RZ1 form (marriage application) and RZ2 forms (declarations of oath), which you will get at the marriage registry in Malta
- Birth certificates
- Free status certificate, or certificate of non impediment - the Embassy of Pakistan in Italy delivers such documents (see here, "Unmarried Certificate"); however depending on your asylum case, it might not be a good thing to visit the Embassy. If you are not sure, I recommend you to get the help of a lawyer or legal aid group.
- Your previous wedding certificate
- The death certificate of your previous wife
I recommend your girlfriend and you to get in touch with the marriage registry in Malta as soon as possible in order to make sure you collect all necessary documents in time.
I hope this helps, don't hesitate to add a comment if you need additional information!
All the best,