Link to annotated image: https://postimg.cc/Wtc7JBD3
Any advise on how to split the data into domains would be helpful and reassuring in my understanding.
*Please, do not plot foliation (Sn) and bedding (S0) in the same stereogram. Each structure should be interpretate individually.
About stereogram interpretation, you should see the book of Marshak & Mitra (1988) that show excelent description about this.
Marshak, S. & Mitra, G. 1988. Basic Methods of Structural Geology. Enlewwod Cliffs, Prentice Hall
However, the best way is observed the relationship between foliations of different order (Sn and Sn+1) and/or foliation and bedding (Sn X S0) in field. This relationship will indicate the vergence. And then, you must proceed to the interpretation of stereogram.
I don't think there are easy way to split. You should to do this manually. I commonly import the data to Excel and classify by domains following the dip direction (or strike), location and, more important, vergence.
And, please, read about the geology of your area before you start. This help a lot. I hope that I could help you. I have listen what I wrote to you several times from my teachers during my graduation :). Best luck in your studies.