How / if to refactor a Delphi program using only forms and data modules

Question

After years of coding Delphi programs as untestable code in forms and datamodules, including global variables, and the only classes are the forms themselves, containing all

Answer 1

To start with I can highly recommend reading the book Refactoring by Martin Fowler.

This will give you a real understanding about how best to sensibly approach introducing changes to the existing (non OO) code to improve maintainability.

I would not look at an ORM until you have a clear understanding about what benefits (if any) one would bring to your application.