I understand where you're coming from - I've worked as an intern on shows where the PSM wasn't given first choice of ASM, as an ASM where the SM had myself or no one, and as a SM on college shows where the choice was between one of two people I'd never met. It's a rough position to be put in, but can be fascinating as a learning process.
MatthewShiner has a good point; if you feel that you can make this a good learning experience for yourself (and, if possible, for Stu and others!) then I would encourage you to try agreeing to the assignment.
If, on the other hand, you feel that you would be putting yourself in danger - emotionally, socially, academically, or otherwise, or that you would be endangering friends/partners - then by all means, skip the TD and go to the Dean or campus mediators/counselors/Ombuds. If Stu's emails were threatening, then you should not be made to work with him, regardless of his requests. If you intend to go to the higher-ranking department folks, bringing this up is the probably most direct way to refuse to work with him (I'm not telling you that you should do this - but, should it come down to proof, then having copies of the emails would not hurt your case). The other points you have listed, while strong in a social context, might not hold up as well in the Dean's office. I understand that this is personal information, and using it to affect changes in show assignments could be uncomfortable; please take it with a grain of salt and trust your instincts.
Best of luck, and keep the SMN posted on the outcome!
Meg