Hello
My thoughts Blow torch [heat source ] to heat up Spacer while avoiding heating lower Bolt section as much as possible. Then use cool liquid to shrink the bolt stem!
I used Cold oil to cool Gearbox out put shaft that was stuck in a bearing, Heated bearing up, cooled shaft, Sharp tap with Hammer via a block of wood and they came apart.The tiny gap that is made by the expansion of the OUTER item in your case the spacer and the contraction of the INNER Stud by the rapid cooling should be enough to break any amount of grip.
Goggles are or course mandatory also nice thick gauntlets as it all gets a bit hot.
