AOB is how the ship views you. So, if you were a (soon to be departed) lookout on your target's deck, where would you see the submarine? In the scenario you set, you would see a submarine on the starboard side, at a 90 degrees angle. So the AOB at the time your target crosses bearing 000 at 90 degrees angle to you is 90 starboard.
I am not sure I understand the second question. Just use the UZO or the binoculars. Once you spot the target, the number you see is its bearing. That is what I think you are calling "scope bearing to target". I don't understand what you mean "my current bearing". Do you mean your heading? Bearing is pretty simple: Just what the scope tells you. If you mean how you can calculate the target's course, that's a whole different story.
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