I think you did the right thing. It sounds like she was just using you anyway. Why not take the security you provide while enjoying the devil may care with the rest. You sound like you are handling it well. Continue to let her see how strong you are.
Is she now making plans to move out? That would be great if she did (and left the kids) so you will have established yourself as primary caregiver without a fight. This may be the impetus she needs to really look at what her life is becoming and turn this around.
The anger part is no big deal. It's not your fault she's mad...she's making her own bed and she has to lay in it.
You cannot be lonely if you like the person you're alone with. Dr. Wayne Dyer