Ah, quick answers. No problem.
1. No/Perhaps*
2. Small dive light lashed to YS-02*
3. No/Yes/No*
There. Quick but probably not that useful. I mean if it were as simple as just a few questions then quick answers could work. Without more fundamentals being understood however your shooting won't be as much fun as it could be and the results will show it. (Not trying to lecture! It just pours out of me sometimes...

)
You asked about holding the camera and a light if you don't have a built in aim light. Depending on the tray setup you have you could buy a focus light that attaches to the tray, with some way to adjust it's aim. If you are down to a week before leaving it probably doesn't allow time to be ordering anything though. You might want to figure some temporary solution like attaching a small dive light to the strobe itself (short bungy?).
If you could easily exchange the YS-02 for the -01 w/ the aim light it might help but for less than the upgrade price you could augment the -02 w/ some sort of lashed on small dive light. You don't really want to aim the strobe dead-on to your subject anyway, to avoid backscatter, but that's the problem with quick answers; they lead to more questions...
The fiber optic mask? If using the YS-01 you really do NOT want your internal strobe illuminating the scene, especially in macro. The Canon housing partially blocks the camera's flash coverage when in close and could create shadow problems. Plus you want to avoid the "straight back from the subject" reflection you get from it, that's when backscatter can show up*. I'd suggest leaving the mask in place and setting the camera flash down to minimal output (it's in Menu). This will also help on battery useage--those NP-6Ls are a bit underpowered IMO. (Uh, you do have extra camera batteries right?)
Whoops, so much for short answers. Have a great time, ask more questions when you get back but also check out the sources listed below when time permits. // ww
* When you get some time, check out UW Photographers Guide
Guide to Underwater Photography | Underwater Photography Guide or Martin Edge's book
The Underwater Photographer.