Hi,
this is usually done by Groovy scripts or with a combination of Groovy scripts and DataSource, DataSource Loop and DataSink TestSteps.
But since you have the .txt file and after a quick look at your requirements I think this couldn't be done, because if I'm not wrong you can only overwrite all data in that file or just append some data to the end of the file, not amend some values in the file.
All the other things in your requirements could be done with a few steps and scripts.
Try to store your data to an Excel file and with this configuration you can easily amend existing data...or maybe the SmartBear Support guys will come up with some pretty good solution.
Regards,
Marek
