Hi,
It seems to me you have done the major part. The start, middle and finish. You have a theme and the plot, turns and twists are there. You would like to refine the characters, create them to be more credible, true to their nature. We need to show character development, how changes, conflict, murder impacts on characters, particularly the main character. How it influences their thinking, attitude and actions.
I am a writer, won a prize in a national drama writing contest in 2008. I am also writing for a local christian blog, active in church and community matters serving as mentor to the youth.
This is your story. I would like to collaborate and help you to realize a dream. This process will take time...there is no quick fix or "take away" solution. We will need to be in constant contact, e mail will help but via Skype will be preferable. To start matters I need to become fully acquainted with your manuscript. Thereafter submit to you a summary, recommendations as well as a framework. Once this meets your expectations we can proceed chapter by chapter.
If you need more information please contact me. Best of luck with your project.