Your approach seems to be the correct one: set the orientation to user-defined and then set the x_angle and y_angle to the desired values.
You can adjust the values for x_angle and y_angle directly in the model using the Reorient command. Go to View menu, expand the Saved Orientations button and select Reorient.

A dialog box called View will pop-up. Change the orientation type from "Orient by Reference" to "Preferences":

Make sure the default orientation is set to "User Defined". Type the values for X and Y angles and hit the Enter button. The model orientation should update.

When you are satisfied with the result write the two values somewhere and close the dialog box (OK or Cancel button)
Now you can go into configuration options and adjust the values for x_angle and y_angle options. The values for this two options are indeed, decimal degrees.
I'm not sure if you will be able to match the orientation from Direct Modeling, but, hopefully, you can get something close enough to be usable.