I could not read you link but looking at the part number I would guess the range is +/- 50A hall sensor. But again I could not connect to your link
From other hall sensors I believe your interpretation is correct.
Sensitivity = 0.625 / 50 = 12.5 mv/a does seem low.
The ACS758LCB-050B-PFF-T has a sensitivity of 40 mv/a. It is not technically non intrusive. But it is isolated and with the only drop being the solder connections and a small amount of board clad.
I'm sure there are others that use coils and do not break the wire. Look at ebay offerings.
You should be aware that hall sensors are stable for sensitivity but have a significant zero drift. You will find for an accurate reading you must periodically read the ~2.5 V when there is known to be no current and compensate for changes.
UPDATE:
If you find a non-contact sensor that is rated for 100A or 150A you can easily use it by running your wire through the center 2 or 3 times. The will increase the sensitivity by a factor of the number of times the wire goes through the sensor. Do not wrap it tight around the sensor, this will result in a sensitivity error.