Hi MU,
I'm sorry your session yesterday didn't go as planned. However, I wouldn't be too hard on yourself. You are dealing with trauma, and it's very scary. I think you have a lot of courage to even try it in the first place.
Your therapists sounds caring. If you're really concerned that he wants to stop working with you, then you might want to try and talk to him about this at some point. Though I know that bringing something like that up is scary in and of itself!
I would think he'd understand if the synergy method isn't possible for you yet due to your having trouble with staying present. I would hope very much that he wouldhelp you work on this so you feel more comfortable before you go to the intern. Please keep us posted and take care of yourself.