You damaged remaining roots and put it under a grow light. This caused severe dehydration.

It's hard to say if you can still save it. But with these steps, you might:

• Place it under a humidity dome (or plastic bag) and mist the dome, not the plant, regularly with distilled water. This allows the plant to breathe again without dehydrating it further.
• Decide what setup you want to use. And then stick with it. Every repotting it highly stressful.
  Since you said semi hydro, do you want to use a submerged setup, or something else? Submerged is best with LECA or bigger pumice rocks.
  Pon or perlite wicks too much when standing in nutrient solution, which will keep the surface constantly wet and causes a toxic fertilizer crust to form, plus algae and mold.
  I also had the experience that they are not aerated enough and I had to struggle with root rot. They require different setups, e.g. Lechuza pots or wicking pots, plus dry periods.
  I personally strongly prefer LECA for myself and my setup.
• You can make use of foliar feeding with highly diluted fertilizer in a spray bottle if you want later. The plant will cannibalize itself to form new roots, and spraying it aids to prevent that. Only do this if you have experience. Same with hormones. Auxins may help, but again, not essential and better used with caution.
• Place it into lower light. The root formation doesn't take lots of light.
• Keep the media moist, but not wet.

All of that is a huge pain. That's why I always try to get cuttings of plants I want first and then, as a second choice, convert it into hydro.