Soft advice, cold turkey or introducing new meimeis (this is the worst cos he will compare them against his "cai", and will result in him yearning for her further which explained why he has no interest in other girls) will not work for such hard core case, one need to help him to rid him of his "Inner Demon (心魔)".
To begin with, it is useful as buddies to assemble a ghost list of the negative things and incidents as mentioned in the thread, go through with him, break it down to him bit by bit cos it wil not be a speedy recovery. Patience is required for success.
消除占有欲, 即可消除心魔
一消心清静, 莲花处处开清 