bella, if we are to be cynical here, then let's approach this from the 'he's being manipulative' angle.
Like all abusive men, they threaten to leave you to reel you back in, this could be the case here, him wanting you to tell him not to do it, then it's your fault it's not done.
I think the best thing is to tell him that even though he's booked this, that you are going to leave, that it's down to him to go through with it or not. That his nicey-nicey behaviour is just that, him behaving, for a while, it's not actually the real him. The real him is the abusive, manipulative, cruel, hurting person. That is the person he is, and that is the person you are leaving.
Let this snip be a catalyst, get the truth out in the open.
Of course, be prepared for his nice phase, as ever, to end at any time. cos it will.