Can the prohibition of פצוע דכא have implications to an already married couple if the husband later accidentally or intentionally became a פצוע דכא?
Yes, in Even Haezer Siman 5 the laws of פצוע דכא are brought. There it clear that even after marriage, one who becomes a פצוע דכא is אסור לבא בקהל and can not remain with his wife. However when this is due to sickness he does not obtain פצוע דכא status. There are many other factors as well which determine whether castration of various methods creates a halachic פצוע דכא.