Humidity too low

Damp moss is better than newspaper for helping that shed.

And, whenever you use a tank you're going to have humidity issues. The best fix, and this is after trying LOTS of things, is the foil treatment. I can send out my tutorial to anyone who wants it, but in PM...it's really long. :) I'll certainly send it along to you, CdnSee.

Plexiglass on top can help as well, but it's more expensive and you can't really get that ventilation opening in the center. Towels are great for boosts to humidity in shed times, but keeping one up there all the time is just asking for bacteria and mold.
Also, keeping the back and sides insulated really helps reduce the need for ambient boosts...and if you do need a lamp, like I do here in winter, the window option in the foil is an asset. :)

I'm going to turn off my lamp tonight and see if the temp stays fine

I haven't done anything special in my BP tank yet, but I also have a CWD, and they need 80%+ humidity at all times, and it took me around a month to get it stabilized. I covered nearly the entire top with scrap pieces of plexi that I had that were the right size. I left an opening in the middle in the front for ventilation, and the part under my hood is also just screen (they need UV). I an still using the screen top, and I have the plexi on top of it rather than underneath sitting in the groove (it didn't work as well that way). I have the plexi (the very thin size) stuck between the screen frame and the screen, and I rarely have to mist anymore. I DO have live plants and a large water area in the CWD tank, but before I set it up like this, I was having to mist constantly and the humidity was staying around 45-50%. Now the humidity stays over 80% where it should be. Before I went with this setup, I used foil, I used plastic wrap, I used glad press and seal wrap, I used a towel (unless you keep it wet it just sucks moisture right back out as it dries), and NOTHING worked.

If you need a vent in a plexi top in the MIDDLE, you might also think about making a wooden top (water treated with something non-toxic) with a vent cut in the middle (cover the hole with screen on the underside, then screw pieces of wood over the edges to keep the snake from being able to get out, I can post a picture of what I mean if you need me to, it is how I installed the screen on my custom wooden hood). You CAN also cut plexi with a dremel (though the friction DOES melt the plexi and send molten pieces of it flying all over the place, so be VERY careful if you try it). Cutting it with a dremel allows you to cut a vent in the middle. I don't really see how cutting a vent in the middle would be necessary, unless you are using heat lights/CHEs and need to keep it from warping/melting the plexi. If you are using UTHs, then all you need to do is drill (or melt with a soldering iron) some vent holes in the plexi (start with fewer and add them as you need to, that way you don't have TOO much ventilation and let all the humidity out again.

I think it would probably disturb the snake, but if not, you could also add a very small bubble stone to the water dish, or build an infuser type thing (no risk of disturbing the snake) with a bottle of water with an airstone inside with a tube going from the bottle into the tank. If you put a valve on the tube going into the tank, you can regulate just how much saturated air is entering the tank. Hope that helps!