The thermostat probe is in a tub, not on the heat tape? As long as it's a vacant tub, sometimes that can fly, sometimes it can't. My first thought is to move the probe onto the heat tape and adjust from there -- give the set up at least an hour or so before checking and making any necessary changes. *But* that really depends on your setup. Either way, you want to regulate the highest temperature your babies can reach.
Something that can help with hides falling is to scoop out is to add some aspen, maybe a quarter inch, to an empty tub. Add the hide. Add the rest of the bedding. I like to pack aspen around and behind hides, as the feeling still provides security, but makes it a lot harder for babies to move the hides too much. I second the suggestion to add cypress to the mix, the different texture might help and more humidity almost certainly will. If it seems like two inches is too much, and it may be, pull back to ~1 inch.
Try not to give in to the temptation of offering food immediately after making changes -- give them a few days, even a week. Posting on Craigslist for mice is a fantastic idea.