When I was a young teen I had a wild coloured rat as a pet. She was amazing temperament-wise. I was able to train her to do tricks, she responded to her name when called (I'd let her free roam quite frequently), and I never had any issues with her.

I am a big believer in personality-traits being inheritable amongst animals. I've seen it with dogs that my family and friends' have bred and I have seen it with an assortment of the crested geckos that I was breeding over the past couple of years. It seems as though you are attempting to have more placid stock, in which case, were it me, I would feed off the mother and any others from that particular line that are exhibiting the more neurotic traits that you're describing and eliminate them from my desired gene pool.