By the end of the war Hitler probably wouldn't have been able to produce the chemical weapons; after the first world war the Geneva Protocol forbade the use of chemical weapons in war (which Germany agreed to) and while Nazi Germany did have extensive knowledge on them, by the end they were struggling to produce rifles.

During the defence of Berlin the German citizenry was armed with low quality k98s, volksgewehr (a cheap rifle based of the mauser rifles), and whatever they could scrounge up. Also even is Hitler had the weapon there probably weren't soldiers willing to use the gas as by the time of the battle most soldiers were old men and boys conscripted in as the last ditch reserves.