As far as I'm aware of, there's no specification in the datasheet about current output node TZ, except for Rt and Ct. No information about current transfer ratio, linear voltage range, bandwidth. Obviously, the datasheet focusses on the regular CFA application of AD844.
Yes - that`s true. Surprisingly, the possible use of the device as a CC is not mentioned in the data sheet - although this feature is exploited by many researchers (and, thus, could be used for promotion of the IC.)