Jesus, that sounds like a nightmare! Hope you get it all sorted out. Probably even more expensive but any potential of suing the developer collectively with the other people? Sounds like they'll have annoyed a lot of people!
Edit: There's an entire article to be written about buying an apartment here when the developer pretty much has a monopoly in this part of the city. For example, you can rarely find a already-built new building (that's not in shambles and will fall at the next big-ish earthquake) to buy. Most people pay for it in advance (before it's even built) and in the end can end up with a shit hole (it happens). And you pay mortgage on a building that's not even completed.