Giving a gecko a sauna shouldn't cause it to drop its tail as long as you don't close the lid on it or something. The gecko in the video didn't drop its tail from a sauna, I think she either came to JB that way or dropped it during a breeding squabble or something, I don't remember. Burrito is one of JB's oldest geckos. lol
I personally prefer paper towels for juvenile cresties over Eco Earth, as there's less risk of impaction.
If your gecko spent all its time burrowing in the substrate then it sounds to me like you've got some serious humidity problems, or there's not enough places in its enclosure for it to hide. Please work on getting some photos up? Pics both of him and of his enclosure might help us identify what's going on.
Temps in the 70s F are ideal for Cresties, but a drop down to 65F at night is fine. As long as you're sure that the heat mat isn't raising the temp higher than 80F down at substrate level, that's fine too.
Do you provide a shallow water dish filled with about 1/2" of clean water at all times? Do you have any sort of humid hide in his enclosure?
It really sounds to me like your guy may have hydration and shed issues, and if he hasn't been climbing since November, this isn't a good sign. My recommendation continues to be to give him a sauna, as it may help and certainly can't hurt. Most of my cresties get saunas about once a week, as that's where I put them while I'm cleaning their cages. I've never had a gecko drop its tail in a sauna and I'm currently running about 30+ in my collection (though there's never any guarantee, of course).
I have a pretty detailed Crestie caresheet on my website-
Crested Gecko Caresheet - Geckos in Tails
Please make sure you and your mom have made time to read through some current and reliable caresheets- most of the info you get from pet stores unfortunately is extremely inaccurate. I'd also highly recommend the caresheets at
Pangea Reptile Supplies Home Page,
JB's Crested Gecko Info, and
Ciliatus.com - The Ultimate Crested Gecko Resource - Home.