It seems you have a lot of questions, so it would be easier for you to check out the wiki:
wiki.andrealphusgames.com
You will find out most of how to date all the girls and their events, and how to augment their submission.
But basically the reason why you fail to get the harems is because you need to:
A: Fill a minimum of submission points on each girl
B: Fill a minimum (usually 45) of "lesbian" points on each girl
If you dont meet those requirements, girls will always fight you for your infidelities and leave you.