Is this safe for beardies?

So I've started making decor for my bearded dragon, I used styrofoam I got from electronics I've ordered, wood glue to attach it all, great stuff expanding foam, then 3 or 4 layers of sanded grout, acrylic paint and then 2 layers of mod podge mixed with water in a spray bottle and then 1 layer of pure mod podge hard coat on the whole thing. My question is, on the corners and a few other places it seems like the grout cracked off and I can see the styrofoam. Since I was done with the whole thing basically I decided to paint over the small openings of styrofoam and the reseal it with mod podge. I also noticed in some of the crevasses there's some areas I missed with grout but I made sure to get with sealant. Is this safe for him to still climb on? What is the real reason for the grout? I know the sealant is because they lick things and it's non toxic for them and all that but I just don't know why the grout goes on there. Is it just to make it hard so it supports them? Also why does it crack off so easily? Is ungrouted styrofoam or expanding foam bad for them? I feel like if someone helps me understand why all these supplies and steps are necessary and what they add to the project I will be able to make better things for him in the future. Thank you to anyone who helps me out! Also is spackling easier than grout? And would it be the same effect as grout?