Please explain in more detain what you mean when you say:
"1.Start address is empty when start and stop address are different."
What is it that you want to do considering this?
2. Rounding is done using the measurement file found in IIS\Resources\Languaged\en-us.measure
In that file, copy & paste the XML for TRACK_DISTANCE, and rename it to REPORT_TRACK_DISTANCE. Change the Format to for example
<Format Format="0.0" />
to round to one digit after the decimal point.
For more info on numering format strings see
Save the measure file. Since measures are cached in the IIS process you may have to recycle the IIS application pool for the changes to take effect.
Now, in the report layout in any the cells that show distance, you should now change unit from TRACK_DISTANCE to your custom formatted REPORT_TRACK_DISTANCE.