Teenage daughters seem to be a tricky parenting or step parenting deal. They can seriously impact all members of the household. Have you looked at books about step parenting or discussed things with anyone from the step family association. I received a little support from them when I was a step mum.
Sounds like you are de-escalating situation and I hop your partner returns with or without daughter and some peace returns.
I dont really know the right way to be on a forum like this either ... like you I just try this and that and hope for the best.
I have had an exhausting but good day. Thanks.