Walnut shell is the deadliest of the lse substrates. It can not only cause an impaction it can perforate the intestinal tract. Please get rid of it. I have some graphic autopsy pictures, if you need to see them.
The Black light is not a UVB and is nothng more than a night time light. I suggest a Reptisun 10.0 T5 Linear tube to run the length of the tank. You also need an incondescent basking light that is full spectrum. The UVB ad basking light need to run 10-12 hours a day. The temps in basking area should be 105-110*F, the ambient temop should be mid 90's and the cool side mid 80's and no lower than 78 at night.
The diet over a year should be 80% veggies to include collard greens, mustard greens, dandlion greens and flowers, esarole, curly endives, greenand red pepers, Butternut or acorn squash. No Tomatoes. The prey items can include all live at 20% of the diet crickets , silk worms, Phoenix worms, and dubia roaches. All foods shuld be dusted with a plan calcium 5 dyas a week asn 2 days a week with a Vitamin. NO Lettuce, it has no nutritional value. No meal worms or super worms.
WE need to correct all thises issues asap.
Now for first aid. Please get the Dragon in a soak of 50/50 warm water and plain pedialyte. This will hydrate the Dragon. While in the soak gently massage the abdonen from snout to vent, This should promote a stool.
THe UVB bulb should also be changed every 6 months.
Hopefully with the proper lighting, diet and supplements the Dragon will respond. Lighting nd temps paly an extreme bearing on activity, appetite and lethargy.
It seems the pet shop gave you very poor information which has put your dragon in jeaopardy.
If the Dragon does not resond to the changes, then a Herp Vet visit will be needed. I can locate some for you with a State or Country.
Please hit reply to discuss this information. I will be happy to assist you.