I highly doubt it's seized. If your rear ended compresses when you sit or push on it it's not stuck. That is the pivot bolt. Meaning the swingarm pivots there and wouldn't pivot if it was stuck. Don't force it out that's not the way to get it out.! I have had my swingarm off plenty and the bolt never moves until you get pressure off of it.
As for the swingarm, I would disconnect the shock from the linkage. And get it out of the way. You will have to use a jack to raise or lower the frame to reach the "sweet spot." Where there is no pressure or tension on the bolt. You should be able to find this spot by trying to turn the bolt as your raising or lowering the frame. Most likely you won't have to raise the frame but you will probably have to lower it down just a tad lower than it sits with the shock on. When you get it to that spot use a punch that is smaller diameter than the bolt and punch it out.