Agree on what AHBD wrote. I'd for sure add that branch.
Also, regarding the thermometer: Many dragons would try climbing the wires. A thermometer that can be reached could either be swallowed (if small), or simply broken. I have a pretty large thermometer, but my dragon always tried to remove it and when he succeeded, to drag it around. (I think he was for some reason annoyed by it.) For checking the temperature, I now put in the temperature and remove it afterwards, instead of constantly monitoring the temperature.
For the substrate: Do you mist it regularly? I have similar substrate and mist it each day (morning) lightly. It should then form a quite hard surface (but still allowing the dragon to dig) when it dries out. I'd recommend doing that already, before you get your dragon.
I could also recommend adding a live plant. The plant "callisia repens" (also sold as "golliwog") is edible for reptiles including bearded dragons. It's quite hardy and survives in a terrarium (so it's not wilting or dying off in that hot and somewhat dry environment), and your dragon can and pretty sure will eat it. You can get it at garden centers.
I always have one in the terrarium since I got my bearded dragon, and it was indeed the first green he ate
My dragon is now an adult, and I have three large plants in rotation; means, if he has eaten about half of the plant in the terrarium, I switch the plant out and the previous plant can regrow on the balcony.
I like it as it has good nutrition values and so my dragon has all day long access to crunchy greens (like many people, I'm not home during the day and so could not offer fresh greens multiple times a day but just in the morning).
