It indeed was a monster of a post, but you write so well that I was able to get through it no problem.
Right where do I start, lets take an offensive to all of this...
First of all, stop with the mental self flagellation! Yes, you made a mistake, in the heat of emotion and pain and hurt you made a mistake, but your human, humans make mistakes a lot, especially if we try to suppress everything that we are feeling.
What has happened is that whilst you endeavoured to support him, in his confused anguish, you suppressed (you call it compartmentalised) your emotions, but that doesn't work. What happens is that it bubbles under the surface until it bursts at the slightest turbulence, in this case, messages on Myspace or facebook.
It is evident your self esteem is non existent, and to be honest this guy is taking advantage of that. If he cannot see in all that time you was together, what we all see by one post, that your a selfless caring individual then he is not worth it.
I think you should tell the truth... For yourself. You don't need his affection or anything from him. You are going to get that from someone, who will truly appreciate you, someone who won't jerk you around, break your heart with callousness and then reel you back in, manipulating your broken soul which was a product of your past.
Your a strong caring girl, and you don't want to lose yourself over this person who is, and will destroy you.
If you ever need to let it all out, then PM
me, and you can write another monster post, I'll read it, even if its not so well crafted as this.