Ents, my bong is stuck. I need your advice/assistance

Basically, our glass on glass beaker bong is stuck, as of yesterday. It is a build-a-bong, and can be smoked either vertically or from the side. That is, there are down-stems and smoking end fixtures for both holes in the beaker. We keep it very clean- change water after every session, clean with alcohol regularly (more care than the other bongs, perhaps). But now it's stuck as fuck.

Anyway, yesterday felt like the first day of spring, so my roommates and I were out in the back yard for most if the afternoon, with the bong, brought it in, and now we can't get the fixtures out. It was set up to smoke from the side with the bowl in the top. When the bowl is in the top there are two G on G down-stems and they're both stuck. The bowl comes out of the slide (14mm) but the slide (18mm) doesn't come out of the downstem (massive, roughly 36-40mm) and the downstem won't come out of the ground joint in the bong. It's almost entirely clean. I feel like the bong has expanded in the sun and then contracted again around the largest joint.

We've tried twisting, with varying amounts of force. We heated water and let it sit in the bong trying to heat the glass. We burned our hands. We tried vegetable oil, then Liquid Wrench. We've poked it from inside to see if pressure applied from in there would loosen it. We let it sit over night. Tried these again. We haven't submerged the whole thing in boiling water yet and we haven't frozen it yet. We haven't taken a blowtorch to it; and refuse to take metal to it. Fuck. Any help? This bong is so frustrating.

TL;DR. My GonG downstem is stuck in my bong, seemingly permanently. EDIT: pic.