you've tried penetrating oil (plusgas not WD40) on the seat post? give it a few days of soaking - you could put a short length off inner tube to create a receptacle for the fluid - use a scribe between the post and the frame to cler any corrosion to allow the fluid to flow between the two.,.
heat - you can go quite host as you have no worries about damaging the paint, then cool totry to break the seat - hold the post end in a vice and try twisting it.
all the fails, then it is caustic soda time.
my 96 killicomp was purple -not sure why yours isn't; it was also for rigid forks.