Islam cares for establishing a lovely relation between a man and his wife. It calls upon both parties to exchange love, show respect, and care for each other. This applies to all aspects of their life: social, intellectual, intimate, etc.
Moreover, Islam pays great attention to the intimate aspect of the husband-wife relationship. Once, when the Prophet got to know that one of his Companions used to spend the whole night in prayer, he immediately gave the Prophetic guidance “Your eyes has a right over you, your guests have a right over you and your wife has a right over you.” (Reported by Al-Bukhari).
In another occasion, the Prophet directed the man to how he should approach his wife, He said: “None of you should fall upon his wife like an animal; but let there first be a messenger between you.” The Companions exclaimed, “What is that messenger?” The Prophet replied, “Kisses and (romantic) words!” (Reported by Al-Daylami)
If these are guidelines on the side of man, the Prophet (peace and blessings be upon him), on the other hand, urged the woman to respond to her husband if he called her to make love. Abu Hurayrah narrated that the Prophet (peace and blessings be upon him) said, “If a husband calls his wife to his bed (i.e. to have sexual relation) and she refuses and causes him to sleep in anger, the angels will curse her till the morning.”
Given these general guidelines, one can conclude that, in response to the specific points indicated in the question, among the duties of a wife towards her husband are that she should satisfy his needs, withhold him from falling into the unlawful and exchange love and affection with him.
If the wife declines his desire to make love with her, he may be psychologically affected and experience physical ailments related to this (e.g. stimulation excitation, congestion and sexual suppression due to the lack of ejaculation).
In the same vein, the wife may go through similar problems and experience the same sufferings if her man declined to meet her sexual needs.
Therefore it is of the wisdom of the Shari`ah that it calls both parties to understand and respond to the natural need of each other. If both husband and wife respond to each other, they will maintain each other’s love, care and affection. Conversely, if they refuse, the relationship can deteriorate. This may also lead one of them to deviate from the right path and look for pleasure outside the marriage. This will eventually lead to the breakdown of the family and the disintegration of the society at large.
However, it is to be added that if the wife is physiologically or physically ill and unable to respond to her husband’s call then he should be considerate of her condition and never harm her in any way.
In this context, the late Sheikh Ibn al-`Uthaymin, the well-known Saudi scholar, adds:

If the wife is psychologically ill and is not able to actively respond to her husband’s call or if she has a physical illness, then in such cases it is not allowed for the husband to call her to bed. This is because the Prophet (peace and blessings be upon him) said “There is to be no harm done or reciprocation of harm.” He should either refrain or enjoy her company in such a way that does not harm her.