Can anyone think of a way to get out of this situation? I'd hate to lose this character, I'm at level 21 with some pretty high grade gear.
There's a lot of ways to get out of that situation, but most of them involve knockback. Stand south of the cake/portal, and hit it north with something that has a knockback effect. There's a decent chance that both items will go the same distance and need to be hit again, so be careful not to slam them into a wall or other terrain feature where they could get stuck. Eventually, one item will fly further than the other, and you'll be able to step onto the portal. If that doesn't work and you're attached to the character enough to try something mildly cheaty to save them, you could launch with -debug-flag and use the "p" button to escape the floor.
Luckily it looks like you've been specializing in polearms. I think there's at least a couple of polearm skills with knockback.
Well, I got the podium off, but now every time I walk onto the portal the game crashes. Sorry, but how exactly does that mildly cheaty thing work?