Being a young teen is really hard, expecially when one parent is just not around.
Are there any older males in the family that your son can get close too? My brother
started acting out after my dad died and my uncle started taking him out to do "guy things"
and it helped him adjust better.
As for calling your ex, I would just try to resume no contact. You called him in a moment
of emotional turmoil with your son and he didn't come through. If he had stepped up
and really did the right thing I could see questioning the no contact, but he proved to be the
same..so you'll prob. save yourself alot of hurt by just resuming no contact.