Can the 2 epics of Homer, and Paradise Lost by John Milton be compared to see the development of morality from Ancient Greece through the Hellenistic period, to the era of Christianity?

Answer 1

The short answer: yes.

The long answer: yes, but it will take a lot of work, and to do it properly, you need to have a knowledge of a variety of texts - epics, philosophical works, political treatises, religious practices, etc. - that you can use to interpret each text independently, and then in conjunction with each other. I personally have not done this research, but there are a good number of texts out there on the history of western ethics. While it might take some digging to find one that starts with Homer instead of Plato (and it might even be better to find a separate book on Homeric ethics), it will give you the historical and philosophical framework to do this. And it will be a massive undertaking.