I know this is bad, but I really want my ex to be fired or transferred to another office.
Why do you want them transferred or fired?
Working in the same building is really uncomfortable.
That sounds like a difficult situation. Maybe you can find a way to avoid them without doing something drastic?
I'm not sure that there's a way to avoid them.
It's very hard to work with an ex partner. Both of you need to be adults and learn to work together peacefully. Talk to human resources about the situation and see what they suggest.