“Is your love so shallow and empty that you aren’t big enough to forgive one mistake”

Stop downplaying this and placing the emphasis on OP to be the “bigger person” and forgive her. You are being quite rude and asking way to much of a person who has just had their heart broken and their world turned upside down due to the biggest betrayal that can occur in a marriage. She did not lie about some minor incident that can be resolved over one conversation. She justified holding it back for 7 years.

“Do you feel less of a man”

you are being incredibly insensitive and yes to certain men it feels like the ultimate betrayal because they think “was I not good enough”, “did I not please her”. It’s up to OP to decide wether he wants to forgive her or not but she does not deserve forgiveness because she just felt guilty. If she is honestly sorry and works toward making it better, how ever long that takes then it might be worth forgiving.

I think the best possible scenario would be they remain together for the families sake, but as OP said he would not be able to let this go and it would always haunt him, I too would urge him to forgive her but this is not a situation that can be taken lightly or brushed off as a simple mistake