1. It could be the Slope Format as set under the Project Options > Units and Format > Slope Format. If you need this to be a percentage output make sure the format is set to "50%" and not a different format as shown in the image below. Then try running the annotation again.
2. There is no option in this command for displaying a terminator on the end of the line displayed. However, you can assign a line style which would have an arrow to indicate the direction. Under the linestyles, try assigning the { Arrow } linestyle which will put the arrow on the line.
