I don't think this is a "horrible keeper" issue at all. I've no doubt that you care a great deal about the well being of your snakes and do your best by them. I think it's more of a "communication" issue. Your first post makes it sound very much like you tried breeding him for the first time last night and threw a bunch of different snakes in there with him with obviously no success. Only after being questioned about it did you say you'd been trying for a month. You say your "only other option" is to throw the six month girl in there with him AS IF that is an option at all. Which obviously it is not. But your post made it sound like you thought it was. That's all.
All I can suggest is to try not to be so stressed about it. I DO understand it can be frustrating when they don't behave as we expect them to, but we have to understand that such things are going to happen. Have you tried contacting the snake's original owner and discussing your concerns with him/her? Maybe they can go over their exact routine that the snake is used to? But even if you get exact instructions...your house smells different...sounds different...feels different. Maybe this is just a very sensitive snake that you'll have to have a lot of patience with to learn what he needs to feel comfortable. It may take longer than the "norm."