Reading your letter made me tired. Have you noticed how much work you are doing? You initiate sex, you are the one who is checking up on his cyber chat habits by contacting the women he talks to, and now you want to know what YOU can do to prevent his having an affair and make the relationship new again. You are working up quite a sweat here, meanwhile, what is he doing to maintain the relationship?
While you play housewife and mother, actress and country girl, he is kicking up his heels and relaxing. If he wants this relationship, he needs to work it with you. Your first step is to put the ball back in his court. Describe his disinterested behavior (that he doesn't approach you for sex, that he is forming ties with other women), then ask him to take responsibility for his actions by directly communicating their meaning. What is he trying to tell you about how he feels about you and the marriage.
What is missing for him? What is it that he expects to get from these other women that he isn't getting from you? How does he want you to interpret his actions and how does he want you to feel about them? Should you be feeling pushed aside and unwanted? Is that how he is feeling? Is he paying you back with disinterested behavior because you are making him angry by not meeting his needs?
By attaching to these other women, he is taking his marital problems outside the relationship. These cyberflirtations may give him a temporary escape or an actual high, but they do nothing to help the marriage. He needs to work with you on improving the relationship. Listen carefully as he explains what you are doing to make him unhappy and what you can do to build a stronger connection.
As he sees that you are responsive, his interest in other women should fade and his interest in sex with you should rise (pardon the pun). All of these changes will insulate you both against an affair.