I think you can make a PC to PC connection, but that means disconnecting PC2 from your wired network since you can't be on both networks at the same time.

I know you don't want to use another device, but why don't you try connecting a wireless router instead of PC2 and then connecting PC2 and your laptop on the wireless connection?

By the looks of your problem, you don't need an expensive wireless router. A small on would do the trick.