Nope you're not blowing it out of proportion.
Your setup is full of the most common issues that cause problems with BPs. Unfortunatly the solution to all the problems requires spending money.
1) humidity gauge. I assume it's a stick-on one. They are 100% completely unreliable and never are accurate. Ditto for those stick-on temperature gauges. You need a digital one. For $15-20 you can get a digital dual thermometer/humidity gauge from wal-mart in their thermometer section.
2) hides. Those log hides don't provide your BP very much security at all. You will want two of them, one on each side of the cage so that when you get an unter tank heater one hide is on a cool side and the other is on the warm side
3) heater. get one. get a thermostat or rheostat(lamp dimmer) to control it, as they can get tremendously hot if left uncontrolled. Thermostats are pricey but PLEASE PLEASE at least get a lamp dimmer. To go along with this you also need an infrared thermometer to measure temperatures over the warm side. There are affordable ones in the $15-20 range. Heat rocks aren't worth spit and run exceedingly hot and may burn your snake.
4) solving humidity. Many pet stores sell a pet-friendly moss (sphagnum moss) that comes in brick form. I like to keep a bunch of this in any reptile cage that requires humidity. Mist it once every day or so, and it holds humidity very well. You already know about covering the top portion of your cage.
If you don't solve all those problems, your snake may very well go dehydrated and underfed as it refuses to eat due to physical and mental stress. Being cold will put it at serious risk for infections.