Writeacher, can you please check these sentences?

1) Joyce's Dubliners focus (or focuses/focusses??) on two recurrent themes:...
2) The epiphany is caused by a trivial gesture, an external event, or a bad situation, (is the comma necessary?) which leads them to a more profound understanding of themselves....
3) Through the telescreen the Thought Police are known to monitor their citizens' actions (??):

1) Joyce's Dubliners focuses on two recurrent themes:...

2) The epiphany is caused by a trivial gesture, an external event, or a bad situation, which leads them to a more profound understanding of themselves...
Yes, the comma is needed.

3) Through the telescreen, the Thought Police are known to monitor their citizens' actions: