Make the affair is unpleasant an experience as you can.. if you out him to family and all of his friends and make it a known fact that you have forgiven him and invite him to work on the marriage he will get a nasty reputation and the only way to save it is to end the affair and come home... otherwise he's the town creep
AND it makes OW look like a sleazy home-wrecker
Infidelity is fun and exciting in secret
Once you out them it becomes a stressful public scandal
"What is best for my kids is best for me"
Persevere = happily being patient over a long period of time