My crimson baby is 7months, she's very jumpy and nervous, but she has never, and probably will never bite. If she would have nipped, she would have nipped me by now I'm sure.
Her mother, crimson as well, is a real sweetheart. Her father is afraid of his own shadow, but even with this fact he only bites when he's in a really bad mood.
I really don't think it's the morph. It's just based off of personality, really.
Handling only twice a week for a few minutes in definitely not enough to tame a nippy snake. As both Sarah and WingedSweetheart said, try everyday that (s)he isn't digesting. I realize that you mentioned the lack of time you have, but even just for 5 minutes everyday rather than twice a week. If your snake was calm, I agree, twice a week is fine, but considering that (s)he needs a little taming, it's just not enough.
Personally, I don't recommend a snake hook. It usually freaks them out a little more, and you don't give them proper support. If you're afraid of being bitten, wear gloves.