How to run 64 bit ATLauncher on i386 debian?
Added (1). I keep running out of RAM every minute, and I have 2GB unallocated, and can't allocate them to minecraft due to me having 32 bit java and ATLauncher. How do I allocate more RAM?
Added (2). I was wondering if I could somehow use multiarch to do this.
You don't, you need a 64 bit operating system.
You can't. I'm not sure if you can do a 64-bit chroot on a 32-bit system (although the reverse is definitely possible). But that's assuming you have a 64-bit processor running a 32-bit OS.
Your best bet is to reinstall a fresh copy of 64-bit Debian (amd64 builds) and start from there.