Chemical stockpiles and reciprocal deterrence in World War II

Did Britain and Germany hold enough chemical and biological weapons for something like mutual destruction in World War II?

Probably. Both held large stockpiles and understood that first use would invite retaliation.

British and German leaders each expected retaliation if chemical weapons were introduced. Large stockpiles therefore created reciprocal danger without requiring the arsenals to be exactly equal. Chemical and biological capacity are not separated in detail. This is a broad strategic judgment about deterrence rather than a quantified comparison.