Harold's willingness to tolerate the verbal attacks of his wife echoes his experience of feeling trapped by an abusive mother. Both women share a very negative opinion of males. As a child, (and now as an adult) it is understandable if he secretly yearned to turn the tables on the punitive, dominating woman. His seeming willingness to "submit to the will of the other" suggests a psychological crouch in preparation before the leap of retaliation. In this context, adultery, can be imagined as an ultimate revenge. Not expressing loving, tender feelings can also be an effective weapon.
Harold may consider himself a superior intellectual warrior, outwitting his wife whose inferior "emotions" can be easily ignited. He also cleverly endorses responsibility to her by remaining "passively indecisive." She can be the "stupid one" who makes the mistakes. They both struggle for the illusion of superiority over the other (seeing each other as "irrational"). His wife's scorn for his "mushy inside" is a typical maneuver of depreciation in a battle for supremacy.
I am quite surprised to find out that Harold is a competent psychotherapist. Perhaps his superior intelligence permits him to make astute diagnoses and interpretations. However, his insensitivity to feelings and emotions must be a handicap in the timing and style of his interventions. I also suspect that he might find it difficult to deal with dominating female clients, either being intimidated by them, or using his position to "outrank" them.
Don's strategy to use Harold's own techniques, in the beginning, to help him feel safer and more comfortable, seems justified. It must have been difficult to keep him on track with his tendency to miss sessions, possibly as a way of expressing control and protest, or out of a fear of dealing with some painful material. Did Harold give a reason for missing the appointments? Eventually, he must have felt a growing confidence in Don's approach to suggest twice a week.
His statement about "not liking to have emotions" seems to be true regarding his avoidance of positive emotions--however, he does not seem to mind harboring a negative emotion like rage. (For some people, rage and hatred are intoxicants that fill them with illusions of power.)
Harold's "wanting to have more fun" may be a superficial compensation for a lack of a deep loving connection in his life. His inability to set limits, for himself or others, suggests a tendency for indulgence that also reflects a core emotional emptiness in him. He is waiting to be filled up from the outside. His boredom and feeling that "there must be more out there" may indicate an inner poverty of positive feeling for himself or others.
His fear of psychotherapeutic enlightenment and a life "without passion" I interpret as a disguised expression of a fear of a life "without real love." I think he doubts that anyone else feels that deep love for him, because he has not yet permitted himself to feel that deep love for others. This is the experience that he needs from a therapist, in the form of a "professional love" that goes beyond intellectual insight and practical problem-solving. (Adler advised us that even a grown man may need, from us, the love and gentleness that a mother would show an infant.)
I would be tempted to use eidetic imagery (using a modification of Akhter Ahsen's diagnostic technique) with Harold. By inviting him to visualize vivid, detailed images of each parent (starting with the mother), progressively deeper feelings can usually be elicited. The experience can be quite revealing and often cathartic. After discussing and interpreting the results, a therapeutic eidetic technique can be used to transform negative, painful images into nurturing, positive ones. Depending on Harold's tolerance for trying unfamiliar strategies, I might also suggest role-playing or narrating a series of "missing developmental experiences" with him.
One potential crisis for Harold in psychotherapy would be seeing himself unmasked. He may think of himself as a kind, rational person, who has been abused and victimized by others. It could be a shock for him to realize that he might be driven by an unconscious, disguised, aggressive goal of burning ambition and revenge, one that needs to be fueled by very strong, hidden, negative feelings.