FreeBSD x86 vs x86-64 Questions about Security

[Jimmy]

Hello,

I Am interested to know several questions..

- Currently I am using FreeBSD x86-64 I have compiled the majority of my 
applications up using the right compiler flags to support the 64bit OS. 
Is there any way within the Operating system that I can turn off 32bit 
support?

- Are applications that have been compiled for the amd-64 platform still 
vulnerable to x86 style attacks because of the backwards compatability 
mode? (eg remote buffer overflows in say.. openssh?).

Thanks

J