Mr. Rebbetzin: I challenge you to name one or two of the allegedly “many great bnei Torah (and even gedolim) of previous generations had wives that did not cover their hair.”
It simply doesn’t exist. You are stretching, by a long long shot, the definition of great Bnei Torah and Gedolim.
And you’d have a hard time finding anywhere where the husband and wife differ about an eiruv. If the husband’s shitta is that the eiruv is invalid, unkosher and Chillul Shabbos, the wife is prohibited from utilizing it. Period.