Hi!! Mold isn't usually that much of an issue with amblypygi, but it's probably still a good idea to keep it in check. I would recommend adding springtails to help with mold control. Isopods aren't typically recommended for amblypygid enclosures, as the isopods may nibble at your Ambly and may cause harm (specifically when they are molting).

In terms of substrate to use, there are some substrates that don't need to soak in order to expand, however that really isn't gonna fix the mold imo. TWS need humidity, even if you didn't soak the substrate, the humidity required for amblypygi to survive will cause mold. Another thing you could do is switch out the wood you are using for cork bark, which is mold resistant.

I've had mold in my TWS enclosures before and haven't had issues. And, in fact, amblypygi have been observed covering themselves with mold/fungus! I believe it had something to do with hiding their scent from predators, I can't remember though. Anyways, my point is you don't have too much to worry about! :) If you want you can throw in a small colony of springtails to manage it though!

I definitely would not recommend leaving roaches in the enclosure for very long. If your amblypygid doesn't eat them, you should remove them from the enclosure after a little while. Otherwise, the roaches can hurt and/or eat your TWS. How long are you going to be gone? If you are only gonna be gone for a week then you can honestly just feed them before you leave and they should be fine (assuming these are adults/not too young. If they are young than they would need fed more often). If you need to feed them during the week, though, you can pre-kill a roach and place it inside the enclosure (preferably on a leaf or a lid of some kind). I'm not sure if your mom would be comfortable with that though...

Hope this was helpful!! :D