Stop beating yourself up. You did what you did. You erred on the side of hoping you could trust him. Now you know for sure you cannot. End of discussion. It's just going to be a further waste of your time and energy to be angry with yourself about it.
Try to look at this development as a new problem with a new set of tasks. See what you can do to speed things along, and don't be afraid to ask people for help. You've been through so much, you can get through this now.