A large discharge in the "key off" position is caused by stuck cutout relay points. Disconnect a battery cable RIGHT NOW, or the battery will discharge itself through the generator and burn both units out. Your "new" regulator is defective and needs to be replaced. A 1/2 volt drop between the regulator BAT terminal and the battery indicates there's a dirty connection somewhere- - - - -at an ammeter connection, or possibly at the battery cable connection at the starter. You should be getting approximately 7.5 volts, measured at the battery posts (not the cable terminals) with the engine running at a fast idle with a fully charged battery if the regulator is adjusted properly.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!