The urp file of a program is located in the program folder of the robot. You can download it using an ftp connexion (user : root / psw : easybot), filezilla works fine. The extension is .urp but in fact you can unzip it. Inside the zip there is an xml file. The first lines of this file describe the DH parameters.
Q1 answer : use in your calculations these parameters ( the controller uses these values)
How do you measure the accuracy in the real world?
It’s normal to do not have the same real position as the controller in the real world. A robot is repeatable (+/-0.1mm announced by UR) but not accurate ( I have in mind minimum 10x it’s repeatability so +/- 1mm in the best case).
hope it will help