What would you or Eugine Nier consider a proper remedy?

I can't speak for Eugine, but I already told you the remedy I think appropriate - ordinary contractual damages. And this would be true not only for adultery, but for any fundamental breach. Of course, parties should be able to specify their own terms as needed in these cases (e.g. liquidated damages). And this needn't even be the default; but the key thing is that at present, if parties want their marriage contract to be meaningful, they are unable to make it so, as the courts will simply disregard any such terms as contrary to public policy. Fortunately the wind is blowing in the right direction (prenuptial agreements) but much too slowly.

Those who prefer a different standard are as free as they always have been to find like-minded partners, arrange things between themselves, keep their own agreements, and find their own social support for them, just as those who would engage in trade in the absence of reliable contract law must create their own arrangements.

You are right that people are able to trade in the absence of government. But government sometimes helps! Despite this, people like yourself have reduced marriage to a kind of Somalia, where people are unable to form enforceable contracts. People who prefer a different standard as you so strangely put it, should be free to form their own contracts.

However,

The guilty party is no longer cut off without a penny, still less forced to wear a scarlet letter, horsewhipped or stoned. If that is a problem, it is not a problem with the law, but of those general attitudes. O tempora! O mores!

I am disinclined to continue a conversation with someone as lacking in basic manners as you.