I had a weird dream where my wife went back to her ex before me. Woke up angry, does that mean anything?

It sounds like you do not know where you stand in regards to your wife's affections. Instead of sad, you wake up mad as a box of frogs! This dream means you are in a quandary about the affections of your wife. Is there any special reason why you would feel this way? Has something happened recently, not necessarily having any connection to her ex, but rather something disconcerting? It may have jarred your faith in your marriage, and caused the dream. Be sure to give her an extra hug and kiss today to let her know she is well loved. You need not tell her about the dream, just be kind and extra loving to her and tell her how special she is to you. This should calm you subconscious mind down a bit and you can sleep easier tonight. I wish you well Chris R.

It would appear that you have issues with the fact that she is still friends with her ex. You feel this has a negative influence towards your relationship and you would like it to end, This is creating anger within. You are being shown this dream so you can realize what is going on in your psyche. Perhaps you need to address this anger before it leads you to impulsive action that would not only be damaging to your relationship, but also your emotional wellbeing.

Probably just you waking up angry because you would be angry if it happened in real life. You can still experience emotions while in a dream so you probably just woke up feeling those emotions still.

Yes, obviously, it means you have some unconscious anxiety about your wife going back to her ex. That's how dreams work.