You can use the protactor (triangle) tool on the map to measure angles. Click in front of your target, then on your target and then on your sub. You should now have one leg extending in front of your target representing it's course, the angle part on your target and a leg extending from the target to your sub. The angle shown is the OAB.
Speed can be determined by placing a mark on your target and starting the stopwatch. Let it run for 3 minutes and place another mark on your target. Measure the distance traveled in yards and divide by 100; 700 yards = 7kts, 1100 yards = 11 kts, etc.
Can't for the life of me remember the exact formula, forgot after installing RFB. I'm sure someone will barge in here to clarify and fill in the details.
You can determine speed from the scope, but this is beyond me. The marks are 4deg for the large ones and 1 deg for the small ones in low magnification, 1deg / 0.25deg in high magnification. Personally I only use them to determine a good angle to use with the offset dial for a nice spread.