Does a man commit a sin by refraining from marrying another woman—despite his ability and desire to do so—in order to preserve his wife's feelings, while he is greatly attracted to women and wishes to have more children?

There is no sin upon you for not marrying a second wife out of consideration for your wife's feelings. Scholars have differed on whether it is more virtuous to restrict oneself to one wife or to practice polygyny. If one wife suffices you and keeps you chaste, then restricting yourself to her is more virtuous according to some scholars, to avoid sin. However, if she does not suffice you, then marrying a second is more virtuous. Ibn 'Uthaymin held the view that restricting oneself to one wife is safer, but if one wife is not enough to keep a man chaste, then he should marry a second, a third, and a fourth. The matter requires a rational balance.