You were right to tell him to limit his calls and visits to you. He no longer has the right to expect you to be available for him 24 hours a day. And for you - you need outings to get you away from staring at the phone. Yes, you feel bad without the contact from him but you know this is the right path if he is ever going to wake up and realise what he is giving up.
Unfortunately I think there is no escape from your sadness at the moment. There may be a certain amount of distraction by visiting friends, etc, but the sadness is something you will have to live with while it runs its course. Accepting that might help you. The good thing is that it will come to an end. One morning you will say to yourself, I am sick of feeling like this, I am not going to waste my emotions on this person any more, and healing will progress another step.
You will not go on feeling like this forever. Ride the storm. If you feel suicidal phone me, or get on line here, but most of all think of your boys. You couldn't do that to them. As much as I know you would die for them if necessary, right now you must stay alive for them. Start eating properly again please.
One day you will know your children saved your life when you were suicidal, just like my daughters did for me years ago. And now here I am, very grateful that I did not throw my life away over someone who was just not worth it.
I now have someone worth dying for: the difference? He would never let me suffer that much. Don't throw away your love any more on someone who can't see its value. Give every little bit of it to your sons.