Toddler started waking in night ?

you seem to have answered your own question, id say its a combination of the points you made. consistancy is important, especially when parents are separated, it becomes difficult. he also could have picked up on your feelings during a very difficult time, even if you tried to protect him from it. it sounds like you're doing all you can. just do your best to make him feel safe and secure but stick at it. not easy at 1am though!