Yes, The BBB is just fine for Hot Tubs;
however, you may want to substitute BROMINE for Bleech.
Bromine is more stable at higher temperatures ( doesn't dissapate as quickly), so it is used more often in hot tubs & stand-alone spas. You can use either, so if you can get bleech really cheaply, you could go that method.

you wanted to know what levels your testing should be:
you may want to check with the manufactor of your tub as they might have specific levels required to maintain warranty,
however this is what is generally accepted:

PH : Between 7.2 to 7.6
TA ( alkalinity) Between 80 to 120
TH ( total hardness) Between 100 - 200
Bromine: 3ppm to 5ppm
TDS ( total dissolved solids): Under 1500ppm

( I prefer to keep my bromine up around 10ppm, but that's considered "high" by industry standards)

You can check throughout the pool forum for information on how to correct your levels using BBB.

( first chance you get, you need to get the sanitizer levels up)

Good Luck & Happy Tubbing