In android does my google account saves my custom words from the dictionary of the keyboard ?
Additionally is there a way to import/export that custom dictionary?
No android doesn't saves your custom words from the dictionary of the keyboard in your Google account .Normally default keyboard doesn't automatically sync your personal(custom) dictionary. But you can email it or make backup of it in sdcard .
Setting -> Keyboard -> Personal Dictionary OR Setting -> Keyboard -> Keyboard Type(eg HTC Sence Input) -> Personal Dictionary