As someone who's had solicitors letters sent to them .... nothing scares someone quite so bad as the threat of spending 6-12-18 months dragging shit through court. With that in mind, i think its best you get some professional advice - you have rights with your child and nobody has any position to fuck about with that at all. Dont try and reason with her... a short sharp shock will probably do wonders. My take anyhow.
I would hate to be in such a bad situation where I had to go to court just to see my son, it must be so hard mate. My advice would try and have a face to face talk with her, and explain why you are needed in your son's life. Tell her it's not about you and her, but your son, and the big gap that would be created if you aren't in his life. Whatever you do, try not to let it get to you in the head! Just be rational all the time, and imo I wouldn't start drinking, or taking drugs atm, because it is far too easy just to fall into that! The next minute you'll be an alcholic! Just keep a straight head most of the time, and no matter how hard it gets, just take a few deep breaths before doing something stupid again.