The bulb will be fine! Some say it can be even better than sunlight! From my personal experience i find Dandelion hard to grow indoors due to their long deep roots.
Make sure he doesn't eat anymore as it's a "do not feed" on the tortoise table. Just try soaking him more than usually to try and wash it out of his system.
Thanks for changing the substrate, for the glass if you put a line of tape around the outside the outside rim to stop him seeing through. If a Tortoise can see through something they believe they can go through it!