When a man shows you who he is, believe him...the first time.
I understand that moving on feels next to impossible...you have memories, history, and the familiarity of a man who you've spent time with.
HOWEVER, you have to understand that when you are moving in the wrong direction - when you are ignoring red flags, rationalizing warning signs, and turning a blind eye to plain old bad behavior - life has a funny way of forcing you to make the change you know you've needed to make all along. Wisdom comes in being strong enough and discerning enough to detach from people and relationships that are no longer serving us. Not every relationship is meant to last forever.
Consider what your life will look like a year from now with this man it. Now consider it without him in it. Which situation, honestly, do you believe gives you the best chance to succeed at being the most accomplished, happy, and peaceful nOt Pocahontas??? It is far better to be alone than in the wrong company. Negative people will tear you down amidst their own destruction, and as you have witnessed, this is a man who will self-destruct if you give him enough time and enough to rope to hang himself.
Do you honestly think that a healthy & sturdy relationship is possible with this man? As a previous poster mentioned, when we have radically different value systems from a significant other, it borders on being impossible to bridge the gap. Relationships and marriages can present their own challenges, even when the 2 people are compatible and are both emotionally healthy. You're losing battles AND the war when you agree to engage yourself in an unhealthy bond with a person who lacks integrity.
I always say that one (fill in positive trait here) person deserves another. So, if you are honest, caring, attentive, and mature, why would you dare cast your pearls before swine by investing time and energy with this man? You have been deluded into thinking that ANY of this is your fault when the issue is clearly his. You can not internalize his issues and then make attempts at solving. Like he said, you can not change him. Understand that your inability to change him is NOT a reflection of you. You have not failed by not being able to force a grown man to choose to love and respect you.
No thought lives in your mind rent free...so decide now how you will proceed. Set the pace. If you are determined to get past it, you will. Plain and simple. If, however, you listen to the unwise friend who advised that you re-enter this poor situation, you will likely find yourself in this same situation 6 months from now...or heck maybe even 6 days from now. Perhaps time alone is what you need to re-center and gather your thoughts...and to realize that PEACE is better than a PERSON.
Forgive my extra long post; I'll say this last thing and be done. Know that no winter lasts forever and no spring skips its turn. By that I mean this too shall pass. Yes, it will hurt like hell for a season, but you WILL come out bigger, better, and stronger if you commit to not allowing anything that does not serve the process of personal growth to get in the way.
On a practical note, I'd highly recommend journaling...get those thoughts OUT. Your mind can play tricks on you and send you in circles when you bottle things up.
Good luck!