You have already cut him out. But if he is chaotic, cruel and destructive -- this likely will not stop him. He will try to force himself in, regardless of your wishes.

[ Baelish draws back from the comfortable closeness to Chilton, stroking his beard idly in thought. ]

What has he done in regards to what transpired? Has he seemed genuinely apologetic? Or has he seemed more like he is trying to cover his tracks when interacting with you? If I were in your shoes, I might suspect instead of planning a betrayal he may be attempting to lure the man with psychiatric expertise into a false sense of security and use that to his advantage. If he has you to vouch for his mental health, after all, then he can more easily move on to gain the trust of others -- to inflict his damage while maintaining a high public opinion.