I agree with the two above me. Maybe I can add some perspective with your questions.
1. Can my boyfriend "emotionally" cheat on me? Does that count?
No. You can emotionally cheat on you though. (I see a pattern developing). If this boyfriend was just a "disposable-boyfriend" would you let yourself get so upset with things? Pretend he's disposable for a day
and see if you lighten up. Yeah, and start hugging other guys if that's what you feel inside.
2. Should I break up with him? Do things seem sketchy? and if so, how do I not come off as a jealous B?
Maybe. Yes. who cares? Actually, start flirting with his sister.
3. Am I over reacting? or do I deserve better?
Yes AND yes.
4. And how do I get this ex-bestfriend out of my life for good? She poisons everything she touches.
What issues does the ex-bestfriend bring you? Prolly what you're dealing with right now. If you deal with those things and emotions inside you, you'll have no need for the ex to shove them in your face.