150 Gallon tank with bio active substrate~*

[Thalatte]

It does look wonderful. Master oogway must be thrilled.
As far as loose mealworms, yes the will eat protein but only if its dead and they have no other food source.
In my 20g long hatchling set up I have a 2in, 3in, and 3.5in boxies that have never been harmed by the darkling beeltes(mealworm beetles) even though I put 50 beetles and 200+ worms in he enclosure. I have seen the bugs eat dead worms and other insects but not a one has eaten the boxies. I don't even know how many are in the larger adult set up or my other tanks.

 

[Rover15]

My box turtles are 1" and 1.5" roughly and until I get a larger set up I wouldn't add worms or bugs.

As for the cat sleeping up there my cat used to do the same thing I assumed it was for the heat or the interest of the snake or gecko (never slept on the yellow foots enclosure) but now that I have the box turtles as well I have all my reptiles in a room with the door closed so the cat can't get at them. I'm working on cleaning up my bacement for a mancave/reptile room again a place where the cat can't get to

 

[Thalatte]

Actually for the smaller box turtles red wigglers are great. Not only woo they not harm your turtles at all but they are an awesome food for hatchlings. They are small but high in protein. If nothing else add only the redwigglers.
Then your soil will be aerated, keeps the gnat population down, prevents molding soil, and fun for babies to dig up.