For your understanding: the LOS displacements are relative to each other and to their flight direction, so its important to set a reference point and combine ascending and descending values to make the values absolute.
After the reference point you can use the formula: LOS displacement / (cos(radians(incidence_angle)) to convert the LOS displacement to vertical displacement. When you have this vertical displacement you can combine the ascending and descending displacement by the mean of the points on the same coordinates, if you dont have both ascending amd descending on the same point you have to drop this point.
You can use the velocity from the csv files from the stamps-visualizer manual to make this all work. I will add the example scripts later when i am on my laptop.
Specifically for your case you can use the coordinates of the gps station in your aoi as reference point.