No, it's not appropriate. Such topics are private and vulgar, and should not be casually discussed in general conversations. It violates the norms of propriety in communication.
It is highly inappropriate. In a relationship or in general social settings, conversations should focus on positive, respectful, and family - friendly topics. Discussing this kind of sexual - related and rather vulgar content can make others uncomfortable and is not in line with good moral and ethical standards.
This is not appropriate at all. A healthy relationship should be based on mutual respect, love, and communication about positive aspects of life such as feelings, dreams, and common interests. Talking about 'big dicks stories' is inappropriate for a wife or anyone in a proper social or family context as it can lead to embarrassment and a negative impact on the relationship and the family environment.