Is it normal to wait 19 days to remove stitches from a lower eyelid blepharoplasty?

While I understand your concern, if you trusted the Dr. to perform your surgery I would also trust him to manage any issues that arise in the postoperative period.  He knows your eyelids better than anyone else And I feel you should trust your judgment at this point.

Everyone varies when as to when they remove the sutures.  Some sutures dissolve on their own, and that process can take anywhere from one week to 4 weeks depending on the patient.  Most of the sutures that we use that are non-dissolvable create very little inflammation so if they stay in longer you should be fine.  If your wound opened in the past, probably a good idea to keep them in a little longer.  

Obviously your surgeon has a special plan for you that is based on your history. At this point, you should follow your surgeon's instructions.