How do I remove these Ikea screws? (studs inside holes)
I would apply a high-strength thread-locking adhesive (e.g. loctite 270) to the inside of the head, reattach the head to the threaded rod (AKA stud), wait many hours, remove bolt.


  LOCTITE 270 is a high-strength threadlocker for maximum efficacy in the securing and sealing of bolts, nuts and studs to prevent loosening due to vibration. The product serves to permanently lock assemblies which must not come loose. It works on all metals, including passive substrates such as stainless steel, aluminium and plated surfaces. It is proven to be tolerant of minor contamination due to industrial oils, e.g. engine oils, corrosion prevention oils and cutting fluids. Can be disassembled by heating to 300°C.


Other brands and products are available



From studying the assembly instructions, it seems to me it is also possible (perhaps even likely) that your furniture can be disassembled without fully extracting the threaded studs - so long as all the heads are removed. 


With the head removed, the clearance hole allows the parts to separate

After disassembly you can use the two-nut trick or locking pliers (vise-grip, mole-grip etc) on the centre of the stud to unscrew the studs.